The Worm Turns

Also known as Qué vueltas da la vida, Una Pozione Combina-Guai, La vendetta del verme

Mad scientist Mickey has just brewed up a potion; to test it out, he squirts it on a fly that's been trapped by a spider, a (regular) mouse being harassed by a cat, then the cat when Pluto goes after it, and Pluto when dogcatcher Pegleg Pete goes after him. Each of the underdogs turns against his tormentor.