The movie is the visualization of the popular song.
Paul Matthews (Tate Donovan) is not that popular with the ladies. He mostly concentrated on his work with primates. One day on a whim he is encouraged to seek a gypsy whom can tell his fortune. In the process she spots his deficiency and prescribes love potion number eight (only in diluted form). He become popular with the opposite sex and aggravated the same sex.
Naturally this discovery is too important to keep to him self; so he recruits a colleague, Diane Farrow (Sandra Bullock). After some monkeying around, the get down to scientific work, he in the girls dorm, she with the prince of England, Prince Geoffrey (Dylan Baker).
Soon they discover their true love but as with real life it gets complicated. Eventually this called for love potion number 9.