Dr. Jekyll (Abbott and Costello)

Dr. Jekyll and his alter ego, Mr. Hyde, is the main villain in the film Abbott and Costello Meet Dr. Jekyll and Mr. Hyde. He is portrayed by Boris Karloff. In this film, Dr. Jekyll uses Hyde to exact vengeance upon others who ridicule his scientific research. He is also in love with his niece Vicky and attempts to murder her new love interest, a reporter named Bruce.

Abbott and Costello play British policemen who are kicked off the force after failing to break up a riot at a women's suffrage demonstration. They realize that capturing Mr. Hyde is the only way they will get their jobs back, but after Costello locks him up, he transforms back into Dr. Jekyll. After Costello drinks a serum in Jekyll's lab that turns him into a giant mouse, they attempt to have Jekyll arrested. He transforms once more (and accidentally transforms Costello as well) and a chase ensues throughout London, ending in Jekyll's death. When Costello (also in the form of Mr. Hyde) is brought into the police station, he too transforms back, but not before biting four policemen and the inspector, turning them all into monsters as well.