diff --git a/src/main/java/com/amihaiemil/versioneye/MkJsonServer.java b/src/main/java/com/amihaiemil/versioneye/MkJsonServer.java
index 90c524a..f9c67a4 100644
--- a/src/main/java/com/amihaiemil/versioneye/MkJsonServer.java
+++ b/src/main/java/com/amihaiemil/versioneye/MkJsonServer.java
@@ -71,6 +71,7 @@ private static void initServer(final Storage storage) {
                     .add("message", "pong")
                     .build()
             )
-            .add("authenticated", Json.createArrayBuilder().build());
+            .add("authenticated", Json.createArrayBuilder().build())
+            .add("users", Json.createArrayBuilder().build());
     }
 }
diff --git a/src/main/java/com/amihaiemil/versioneye/MkNewUser.java b/src/main/java/com/amihaiemil/versioneye/MkNewUser.java
new file mode 100644
index 0000000..b0ba31d
--- /dev/null
+++ b/src/main/java/com/amihaiemil/versioneye/MkNewUser.java
@@ -0,0 +1,135 @@
+/**
+ * Copyright (c) 2017, Mihai Emil Andronache
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ * Redistributions of source code must retain the above copyright notice, this
+ *  list of conditions and the following disclaimer.
+ *  Redistributions in binary form must reproduce the above copyright notice,
+ *  this list of conditions and the following disclaimer in the documentation
+ *  and/or other materials provided with the distribution.
+ * Neither the name of the copyright holder nor the names of its
+ *  contributors may be used to endorse or promote products derived from
+ *  this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+package com.amihaiemil.versioneye;
+
+import javax.json.Json;
+import javax.json.JsonArray;
+import javax.json.JsonArrayBuilder;
+import javax.json.JsonObject;
+import javax.json.JsonValue;
+
+/**
+ * Mock user sign-up form.
+ * @author Mihai Andronache (amihaiemil@gmail.com)
+ * @version $Id$
+ * @since 1.0.0
+ */
+final class MkNewUser implements NewUser {
+
+    /**
+     * VersionEye server.
+     */
+    private MkServer server;
+    
+    /**
+     * This user as JsonObject.
+     */
+    private JsonObject json;
+    
+    /**
+     * Ctor.
+     * @param server VersionEye server.
+     */
+    MkNewUser(final MkServer server) {
+        this(server, Json.createObjectBuilder().build());
+    }
+    
+    /**
+     * Ctor.
+     * @param server VersionEye server.
+     * @param newUser The new user as json.
+     */
+    MkNewUser(final MkServer server, final JsonObject newUser) {
+        this.server = server;
+        this.json = newUser;
+    }
+    
+    @Override
+    public String fullName() {
+        return this.json.getString("fullname");
+    }
+
+    @Override
+    public String username() {
+        return this.json.getString("username");
+    }
+
+    @Override
+    public JsonObject json() {
+        return this.json;
+    }
+
+    @Override
+    public NewUser fullName(final String fullName) {
+        final String username =  this.json.getString("username", "");
+        final JsonObject edited;
+        if(username.isEmpty()) {
+            edited = Json
+                .createObjectBuilder()
+                .add("fullname", fullName)
+                .build();
+        } else {
+            edited = Json
+                .createObjectBuilder()
+                .add("username", username)
+                .add("fullname", fullName)
+                .build();
+        }
+        return new MkNewUser(this.server, edited);
+    }
+
+    @Override
+    public NewUser username(final String username) {
+        final JsonObject edited = Json
+            .createObjectBuilder()
+            .add("username", username)
+            .add("fullname", this.json.getString("fullname", ""))
+            .build();
+        return new MkNewUser(this.server, edited);
+    }
+
+    @Override
+    public User signUp() {
+        final JsonArray registered = this.server.storage().build()
+            .getJsonArray("users");
+        final JsonArrayBuilder users = Json.createArrayBuilder();
+        for(final JsonValue user: registered) {
+            users.add(user);
+        }
+        users.add(
+            Json.createObjectBuilder()
+                .add(
+                    this.json.getString("username"),
+                    this.json
+                )
+        );
+        this.server.storage().add("users", users.build());
+        return new MkUser(this.server, this.json.getString("username"));
+    }
+
+}
diff --git a/src/main/java/com/amihaiemil/versioneye/MkUser.java b/src/main/java/com/amihaiemil/versioneye/MkUser.java
new file mode 100644
index 0000000..e47ce5e
--- /dev/null
+++ b/src/main/java/com/amihaiemil/versioneye/MkUser.java
@@ -0,0 +1,120 @@
+package com.amihaiemil.versioneye;
+
+/**
+ * Copyright (c) 2017, Mihai Emil Andronache
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ * Redistributions of source code must retain the above copyright notice, this
+ *  list of conditions and the following disclaimer.
+ *  Redistributions in binary form must reproduce the above copyright notice,
+ *  this list of conditions and the following disclaimer in the documentation
+ *  and/or other materials provided with the distribution.
+ * Neither the name of the copyright holder nor the names of its
+ *  contributors may be used to endorse or promote products derived from
+ *  this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+import java.io.IOException;
+
+import javax.json.Json;
+import javax.json.JsonArray;
+import javax.json.JsonObject;
+
+/**
+ * A mock VersionEye user.
+ * @author Mihai Andronache (amihaiemil@gmail.com)
+ * @version $Id$
+ * @since 1.0.0
+ *
+ */
+final class MkUser implements User {
+
+    /**
+     * VersionEye server.
+     */
+    private MkServer server;
+    
+    /**
+     * This user's username.
+     */
+    private String username;
+    
+    /**
+     * Ctor.
+     * @param server VersionEye server storage.
+     * @param username The user's username.
+     */
+    MkUser(final MkServer server, final String username) {
+        this.server = server;
+        this.username = username;
+    }
+
+    @Override
+    public UserData about() throws IOException {
+        UserData about = null;
+        final JsonArray online = this.server.storage().build()
+            .getJsonArray("authenticated");
+        for(int idx = 0; idx < online.size(); idx++) {
+            final JsonObject authenticated = online.getJsonObject(idx);
+            if(authenticated.getJsonObject(this.username) != null) {
+                about =  new JsonUserData(
+                    Json.createObjectBuilder()
+                        .add(
+                            "fullname",
+                            authenticated.getJsonObject(this.username)
+                                .getString("fullname")
+                        ).add(
+                            "username",
+                            authenticated.getJsonObject(this.username)
+                                .getString("username")
+                        )
+                        .build()
+                );
+            }
+        }
+        final JsonArray users = this.server.storage().build()
+            .getJsonArray("users");
+        for(int idx = 0; idx < users.size(); idx++) {
+            final JsonObject user = users.getJsonObject(idx);
+            if(user.getJsonObject(this.username) != null) {
+                about = new JsonUserData(
+                    user.getJsonObject(this.username)
+                );
+            }
+        }
+        if(about == null) {
+            throw new IllegalStateException(
+                "User " + this.username + " not found."
+                        + " You have to register it first, "
+                        + "or it has to be the authenticated user."
+            );
+        }
+        return about;
+    }
+
+    @Override
+    public Comments comments() {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+    @Override
+    public Favorites favorites() {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+}
diff --git a/src/main/java/com/amihaiemil/versioneye/MkUsers.java b/src/main/java/com/amihaiemil/versioneye/MkUsers.java
new file mode 100644
index 0000000..cea9466
--- /dev/null
+++ b/src/main/java/com/amihaiemil/versioneye/MkUsers.java
@@ -0,0 +1,62 @@
+/**
+ * Copyright (c) 2017, Mihai Emil Andronache
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ * Redistributions of source code must retain the above copyright notice, this
+ *  list of conditions and the following disclaimer.
+ *  Redistributions in binary form must reproduce the above copyright notice,
+ *  this list of conditions and the following disclaimer in the documentation
+ *  and/or other materials provided with the distribution.
+ * Neither the name of the copyright holder nor the names of its
+ *  contributors may be used to endorse or promote products derived from
+ *  this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+package com.amihaiemil.versioneye;
+
+/**
+ * Mock of VersionEye's Users API.
+ * @author Mihai Andronache (amihaiemil@gmail.com)
+ * @version $Id$
+ * @since 1.0.0
+ *
+ */
+final class MkUsers implements Users {
+
+    /**
+     * VersionEye server.
+     */
+    private MkServer server;
+    
+    /**
+     * Ctor.
+     * @param server VersionEye server storage.
+     */
+    MkUsers(final MkServer server) {
+        this.server = server;
+    }
+
+    @Override
+    public User user(final String username) {
+        return new MkUser(this.server, username);
+    }
+
+    @Override
+    public NewUser register() {
+        return new MkNewUser(this.server);
+    }
+
+}
diff --git a/src/main/java/com/amihaiemil/versioneye/MkVersionEye.java b/src/main/java/com/amihaiemil/versioneye/MkVersionEye.java
index 68d8364..7fd8a7c 100644
--- a/src/main/java/com/amihaiemil/versioneye/MkVersionEye.java
+++ b/src/main/java/com/amihaiemil/versioneye/MkVersionEye.java
@@ -39,9 +39,8 @@
  * @author Mihai Andronache (amihaiemil@gmail.com)
  * @version $Id$
  * @since 1.0.0
- * @todo #13:30min/DEV Continue implementing the mock API.
- *  Mocks for Users, Organizations Teams etc are needed. This puzzle
- *  was readded after being removed by mistake.
+ * @todo #72:30min/DEV Continue implementing the mock API.
+ *  Mocks for Organizations, Teams etc are needed.
  */
 public final class MkVersionEye implements VersionEye {
 
@@ -61,6 +60,7 @@ public final class MkVersionEye implements VersionEye {
     public MkVersionEye() {
         this.server = new MkJsonServer();
     }
+    
     /**
      * Ctor.
      * @param authenticated Mock Authenticated User.
@@ -89,7 +89,7 @@ public Services services() {
 
     @Override
     public Users users() {
-        return null;
+        return new MkUsers(this.server);
     }
 
     @Override
@@ -107,7 +107,7 @@ public Me me() {
      * @param authenticated The user to authenticate.
      */
     private void authenticate(final Authenticated authenticated) {
-        JsonArray online = this.server.storage().build()
+        final JsonArray online = this.server.storage().build()
             .getJsonArray("authenticated");
         final JsonArrayBuilder users = Json.createArrayBuilder();
         for(final JsonValue user: online) {
diff --git a/src/main/java/com/amihaiemil/versioneye/NewUser.java b/src/main/java/com/amihaiemil/versioneye/NewUser.java
new file mode 100644
index 0000000..b5e0d18
--- /dev/null
+++ b/src/main/java/com/amihaiemil/versioneye/NewUser.java
@@ -0,0 +1,57 @@
+/**
+ * Copyright (c) 2017, Mihai Emil Andronache
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ * Redistributions of source code must retain the above copyright notice, this
+ *  list of conditions and the following disclaimer.
+ *  Redistributions in binary form must reproduce the above copyright notice,
+ *  this list of conditions and the following disclaimer in the documentation
+ *  and/or other materials provided with the distribution.
+ * Neither the name of the copyright holder nor the names of its
+ *  contributors may be used to endorse or promote products derived from
+ *  this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+package com.amihaiemil.versioneye;
+
+/**
+ * User sign-up form.
+ * @author Mihai Andronache (amihaiemil@gmail.com)
+ * @version $Id$
+ * @since 1.0.0
+ */
+public interface NewUser extends UserData {
+
+    /**
+     * Specify the user's full name.
+     * @param fullName Given full name.
+     * @return SignUpForm.
+     */
+    NewUser fullName(final String fullName);
+    
+    /**
+     * Specify the user's username.
+     * @param username Given username.
+     * @return SignUpForm.
+     */
+    NewUser username(final String username);
+    
+    /**
+     * Sign up.
+     * @return User.
+     */
+    User signUp();
+}
diff --git a/src/main/java/com/amihaiemil/versioneye/RtUsers.java b/src/main/java/com/amihaiemil/versioneye/RtUsers.java
index e0ae046..b20b573 100644
--- a/src/main/java/com/amihaiemil/versioneye/RtUsers.java
+++ b/src/main/java/com/amihaiemil/versioneye/RtUsers.java
@@ -56,4 +56,12 @@ public User user(final String username) {
         return new RtUser(this.req, username);
     }
 
+    @Override
+    public NewUser register() {
+        throw new UnsupportedOperationException(
+            "Users#register() is only available in the mock version"
+            + "of the API yet"
+        );
+    }
+
 }
diff --git a/src/main/java/com/amihaiemil/versioneye/Users.java b/src/main/java/com/amihaiemil/versioneye/Users.java
index d1628aa..3128025 100644
--- a/src/main/java/com/amihaiemil/versioneye/Users.java
+++ b/src/main/java/com/amihaiemil/versioneye/Users.java
@@ -42,4 +42,10 @@ public interface Users {
      * @return A VersionEye user.
      */
     User user(String username);
+    
+    /**
+     * Create a new VersionEye account.
+     * @return NewUser for signup.
+     */
+    NewUser register();
 }
diff --git a/src/test/java/com/amihaiemil/versioneye/MkUsersTestCase.java b/src/test/java/com/amihaiemil/versioneye/MkUsersTestCase.java
new file mode 100644
index 0000000..c493eb4
--- /dev/null
+++ b/src/test/java/com/amihaiemil/versioneye/MkUsersTestCase.java
@@ -0,0 +1,107 @@
+/**
+ * Copyright (c) 2017, Mihai Emil Andronache
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ * Redistributions of source code must retain the above copyright notice, this
+ *  list of conditions and the following disclaimer.
+ *  Redistributions in binary form must reproduce the above copyright notice,
+ *  this list of conditions and the following disclaimer in the documentation
+ *  and/or other materials provided with the distribution.
+ * Neither the name of the copyright holder nor the names of its
+ *  contributors may be used to endorse or promote products derived from
+ *  this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+package com.amihaiemil.versioneye;
+
+import java.io.IOException;
+
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
+import org.junit.Test;
+
+/**
+ * Unit tests for {@link MkUsers}.
+ * @author Mihai Andronache (amihaiemil@gmail.com)
+ * @version $Id$
+ * @since 1.0.0
+ *
+ */
+public final class MkUsersTestCase {
+
+    /**
+     * MkUsers can fetch the authenticated user.
+     * @throws IOException If something goes wrong.
+     */
+    @Test
+    public void returnsAuthenticatedUser() throws IOException {
+        MkAuthenticated authenticated = new MkJsonAuthenticated();
+        authenticated = authenticated.fullName("Mihai Andronache")
+            .username("amihaiemil")
+            .email("amihaiemil@gmail.com")
+            .admin(false)
+            .deleted(false)
+            .enterpriseProjects(1)
+            .rateLimit(50)
+            .compLimit(50)
+            .active(true);
+        User fetched = 
+            new MkVersionEye(authenticated).users().user("amihaiemil");
+        MatcherAssert.assertThat(
+            fetched, Matchers.notNullValue()
+        );
+        MatcherAssert.assertThat(
+            fetched.about().username(), Matchers.is("amihaiemil")
+        );
+        MatcherAssert.assertThat(
+            fetched.about().fullName(), Matchers.is("Mihai Andronache")
+        );
+    }
+    
+    /**
+     * MkUsers can return a registered user which is not authenticated.
+     * @throws IOException If something goes wrong.
+     */
+    @Test
+    public void returnsRegisteredUser() throws IOException {
+        final VersionEye versioneye = new MkVersionEye();
+        final User registered = versioneye.users().register()
+            .fullName("Jeff Doe")
+            .username("jeff")
+            .signUp();
+        final User fetched = versioneye.users().user("jeff");
+        MatcherAssert.assertThat(
+            fetched.about().json(),
+            Matchers.equalTo(registered.about().json())
+        );
+        MatcherAssert.assertThat(
+            fetched.about().username(), Matchers.is("jeff")
+        );
+        MatcherAssert.assertThat(
+            fetched.about().fullName(), Matchers.is("Jeff Doe")
+        );
+    }
+    
+    /**
+     * An exception is thrown if the user is not found.
+     * @throws IOException If something goes wrong.
+     */
+    @Test (expected = IllegalStateException.class)
+    public void throwsExceptionOnMissingUser() throws IOException {
+        new MkVersionEye().users().user("jeff").about();
+    }
+
+}