User JS
User John Sheppard, also known as JS or Grimlock, was a rogue User. After a feud he had with User 553 turned nasty, both Users were punished. 553's soul was forcibly removed from his body, whereas JS was imprisoned. He was briefly freed when Blackout attacked BZPower, but was knocked out by User Shroom and returned to prison.
He escaped again when the Battle of the BZP Staff HQ left his prison virtually unguarded. He tried to help User Kon fight Black Six, but was quickly knocked out.
In the chaos that followed the battle, JS managed to leave the planet. He changed his name to Grimlock to avoid detection, and abandoned his pseudo-anarchistic ways. When User Kon retired and tried his hand at online dating, Grimlock pretended to be a woman and arranged a date with Kon solely to troll him.
A couple of years later, he returned from obscurity to attack the User HQ in a giant Lenin head. Why? We don't know.
Even later, he returned, only to instantly transform into his new identity; Space Pirate Captain Eurobeat.