The Rehabilitator is a device mentioned by the Helmeted Author first during the Arrival of Mynd storyline on October 20, 2001. According to Dave's commentary, it might be a device that simulates the person inside's (I'm asuming there is an inside) worst fear. For example, if George was hooked up to the Rehabilitator, a time travel mishap might cause ice cream to never be invented. For Bob, he could be transported to an episode of Pokémon. The Rehabilitator has never been shown and only been speculated about, but whatever it does, it is most definitely NOT fun to mess with.