In search of an answer to that seemingly simple question, Carl, a curious child, sets off on a great voyage of discovery. As one question is answered, more appear. Soon enough, where once stood but a curious boy, a great scientist will rise.

Turtles Forever is a made-for-tv animated movie. Produced in celebration of the 25th anniversary of the Teenage Mutant Ninja Turtles franchise, the movie teams up different incarnations of the titular heroes—chiefly the light-hearted, child-friendly characters from the 1987 animated series and the darker cast of the 4Kids' own 2003 animated series—in an adventure that spans multiple universes.

One night of severe rain, Sonic and Chip come by an old mansion where they decide to take shelter. Whilst Sonic seems unfazed by the creepy surroundings, Chip is scared out of its wits. The mansion is inhabited by three scary - yet sweet - ghosts who like to play tricks on innocent visitors: A cute and girlish ghost who likes to collect photographs of her terrified guests. The remaining two boy ghosts compete for her attention by taking photographs of their scare victims. Their scariness is the key to popularity in the realm of ghosts. The boy ghosts are excited at the prospect of hunting their new and unusual guests, Sonic and Chip. Who will win the ultimate competition to her heart?

The Conductor assigns Benny the Bear to take care of the Music Machine. However, because he lacks self-control, Benny disappears to find some honey and leaves the Music Machine unattended. Will Benny's enormous appetite for honey endanger Agapeland and help Mr. Pimms wreck the Music Machine forever?