Weird Science 3x11

Lisa shows Gary what's going to happen in the future, only to reveal that Wyatt will end up stealing Gary's date to the prom. Wyatt tries to change the outcome of the future by having Lisa give him the worst personality that she can create. She zaps up a pair of magical Chett underwear, giving Wyatt Chett's personality. Unfortunately, Gary's date likes the new Wyatt even more and Chett is happy because his brother is finally becoming cool.