After a night of drinking Guiness at the local watering hole, an ordinary, working-class, family man in Dublin's life is turned upside-down when he wakes up as a rat.

A pair of aliens arrive on Earth to prepare for invasion, but crash instead. With enormous cone-shaped heads, robotlike walks and an appetite for toilet paper, aliens Beldar and Prymatt don't exactly blend in with the population of Paramus, N.J. But for some reason, everyone believes them when they say they're from France.

Miles Harding buys a state-of-the-art computer that starts expressing conscious thought and emotion after an interaction with spilled champagne. Things begin getting out of hand when both Miles and Edgar, the computer, fall in love with beautiful neighbor Madeline Robistat.