Captain Underpants and the Tyrannical Retaliation of the Turbo Toilet 2000 by Dav Pilkey.
(Blurb)When the Incredible Robo-Plunger defeated the evil Turbo Toilet 2000, George and Harold thought their toilet troubles were over. Unfortunately, their porcelain problems were only beginning . . .
Just when you thought it was safe to flush . . .
The Turbo Toilet 2000 strikes back! The carnivorous commode known for devouring everything in its path has built up a real appetite . . . for REVENGE! Join Captain Underpants for another epic showdown of Wedgie Power vs. Potty Power as our tighty-whitey-wearing superhero GOES TO ELEVEN!