|Eddie Murphy||Professor Sherman Klump/Buddy Love/Lance Perkins/Cletus 'Papa' Klump/Anna Pearl 'Mama' Jensen Klump/Ida Mae 'Granny' Jensen/Ernie Klump, Sr.|
|Jada Pinkett||Carla Purty|
|James Coburn||Harlan Hartley|
|Larry Miller||Dean Richmond|
|Dave Chappelle||Reggie Warrington|
|Patricia Wilson||Dean's Secretary|
|Jamal Mixon||Ernie Klump Jr.|
Brilliant and obese scientist Sherman Klump invents a miraculous weight-loss solution. After a date with chemistry student Carla Purty goes badly, a depressed Klump tries the solution on himself. Though he instantly loses 250 pounds, the side effects include a second personality: an obnoxiously self-assertive braggart who calls himself Buddy Love. Buddy proves to be more popular than Sherman, but his arrogance and bad behavior quickly spiral out of control.