The Ghost: Slimer (Voice of Ivan Reitman)

Helpful How? There are many reasons to dislike the GB sequel - it's largely a lesser retread of the first film, everyone seems to be cashing a paycheck, the villain's a bit cack who never lives up to his legend - but there's still Slimer, who steals every scene he's in.

Apparently having moved in to the 'Busters firehouse base, he makes a small nuisance of himself by stealing food and scaring Louis Tully (Rick Moranis). But he later proves useful by, er, driving a bus to help Louis get to the art museum to help the guys.

All right, so he's not *that* useful. But he's funny.

Frightening Fact: Co-writer/star Dan Aykroyd would refer to the ghost on set as the spirit of John Belushi. He's technically named Onionhead, because of his noxious smell, but that's never used in the film itself.