The writer revealed on the Panel Borders podcast that old characters from the E4 drama could return in the spinoff movie.
"I've written the first draft of the script and we'll see what happens," Overman said.
"If it happens, it will involve past and present characters, I'm not allowed to give away anything more than that."
However, Overman later named Iwan Rheon's Simon and Antonia Thomas's Alisha as two departed figures who could potentially reappear.
"Whether or not you've completely seen the end of Simon and Alisha, if our movie has its way, is another issue," Overman teased.
The fourth series of Misfits currently airs on Sunday nights on E4, with the final original cast member - Nathan Stewart-Jarrett (Curtis) - exiting the show in a recent episode.
A US TV remake of the comedy-drama is also reportedly in the works, with production expected to begin in late 2012 or early 2013.
> Misfits 4.05 review: A death in the family and strange desires
Watch a clip from the next episode of Misfits below (Warning: Contains strong language):