Marvo the Meanie was a magician-like monster. Rito planned to turn the Ninja Rangers into monsters, but since he had Zedd's staff pointed the wrong way, its energy turned Mr. Wilton, a teacher that switched places with Rocky, into a monster instead. Marvo turned all the rangers except Rocky into containers of liquid. Rocky had to turn the rangers back to normal before destroying Marvo because they would stay that way if he didn't. When Marvo was finished by Ape Ninjazord, he turned back to Mr. Wilton.
The monster was resurrected, most likely without Mr. Wilton, as an audience member in the Machine Arena and made several other cameos.