The Racket Buster is a 1949 animated short. It is the 54th cartoon short of the Mighty Mouse theatrical series.
Gangster cats use all means necessary to gather up as many mice as they can find. A gangster cat sees a chance to get even with Mighty Mouse. A movie theater is showing a Mighty Mouse cartoon, and at the end, Mighty Mouse himself is to come out and take a bow. The gangsters grab Mighty Mouse, bind him, and put him in a big safe wrapped with locked chains, dropping it to the ocean floor.... Oh, dear, what is the champion of justice to do? Then they kidnap Pearl Pureheart, and he gets out of the safe to give chase. The head gangster now jumps in a rocket ship with the girl and shoots bullets out of guns in the rocket ship until he knocks Mighty Mouse out and he falls on a star... which he then turns into his own flying machine. Then he shoots bullets out of it (very unusual for Mighty Mouse) to get the head gangster to finally give up the girl. Pearl is enthusiastic and the episode fade out as she's smothering the hero with kisses.