Evil Robot Helmet

The Evil Robot Helmet is the main antagonist of the Grojband episode "Helmet". The helmet is worn by Corey when his voice cracks, so the Grojband members decide to let him wear the helmet. One of the Grojband members accidentaly set the helmet to "Bad Mode", causing the helmet to possess Corey and turn evil. The Grojband members manage to pry the helmet off Corey but the evil helmet decides to fuse with the many attractions at the carnival to create a giant robot body for it. After Trina Riffin calms down from her "Furious Diary Mode," the Grojband members get her diary as lyric inspiration for their song, causing the robot helmet to get destroyed and explode after listening to the lyrics.

Personality
When switched to "Bad Mode," the robot helmet becomes evil.

Trivia

 * He sounds similar to villains like Soundwave from "Transformers" and Drill-X from "Skylanders Giants."