When timid bank clerk Stanley Ipkiss discovers a magical mask containing the spirit of the Norse god Loki, his entire life changes. While wearing the mask, Ipkiss becomes a supernatural playboy exuding charm and confidence which allows him to catch the eye of local nightclub singer Tina Carlyle. Unfortunately, under the mask's influence, Ipkiss also robs a bank, which angers junior crime lord Dorian Tyrell, whose goons get blamed for the heist.

Tim Avery, an aspiring cartoonist, finds himself in a predicament when his dog stumbles upon the mask of Loki. Then after conceiving an infant son "born of the mask", he discovers just how looney child raising can be.