The Bathmobile is a speeding wheeled bathtub combined with a toilet and sink. The words "The Bathmobile" are written on the side of the bathtub, presumably in Zombeh blood.
It first appeared in Zombeh Nation when Edd, Tom and Tord fly out of the door of the Zombeh-infested old house. The vehicle was Tom's idea for his escape plan to get out of the house. A pitch-shifted version of "Running in the 90s" by Maurizio De Jorio plays in the background as the Bathmobile speeds away.
The Bathmobile also appears in the opening sequence of The End (Part 1).