Captain Underpants and the Revolting Revenge of the Radioactive Robo-Boxers

When we last saw our heroes, George and Harold, they had been turned
into evil zombie nerds doomed to roam a devastated, post-apocalyptic
planet for all eternity. But why, you might ask, didn't the
amazing Captain Underpants save the boys from this frightening
fate? Because Tippy Tinkletrousers and his time-traveling hijinks
prevented George and Harold from creating Captain Underpants in
the first place! Now, having changed the course of human history
forever, they'll have to figure out a way to CHANGE IT BACK.

Could this be the end for Captain Underpants?!!