After the defeat of Professor Poopypants. Captain Underpants, George and Harold must stop the hungry Talking Toilets before they eat every human on Earth.

Based on the worldwide phenomenon (again), George Beard and Harold Hutchins borrow a time machine from Melvin Sneedly and accidentally disobey his one rule: don't use it 2 times in one day. Now, they enter an alternate universe where all the teachers are actually nice including Mr. Krupp. But Now, they must face a new enemy -- themselves. George and Harold are evil in that alternate universe and they have created Captain Blunderpants, an evil version of Captain Underpants. Now, they must find a way to escape back to their own universe before Evil George and Evil Harold find a way to escape to their good dimension.—David Soren