|Robin Williams||Professor Philip Brainard|
|Marcia Gay Harden||Dr. Sara Jean Reynolds|
|Christopher McDonald||Wilson Croft|
|Raymond J. Barry||Chester Hoenicker|
|Wil Wheaton||Bennett Hoenicker|
|Edie McClurg||Martha George|
|Scott Martin Gershin||Flubber (voice)|
Professor Philip Brainard is experimenting with new kinds of energy, and he thinks this project will save struggling Medfield College, where his girlfriend, Sara, is president. But when he discovers a lively, rubber-like substance dubbed ''flubber,'' he gets so excited, he absent-mindedly misses his own wedding. Sara dumps him, so he tries to use his discovery to win her back; unfortunately, the mischievous flubber seems to have a mind of its own.