Swayne’s Rats and Cats (sometimes spelled Swain’s, sometimes remembered as Nelson’s) was a notorious animal act of late vaudeville, late enough that it was fondly recalled by many major twentieth century stars in their anecdotes. One finds accounts of the act in the writings and utterances of George Burns, Groucho Marx, Fred Allen, June Havoc, and Mousie Garner, et al. At the climax of the act the rats, dressed as little jockeys, would ride the cats around a little racetrack. Several have told the story in which Fanny Brice retired to find a rat in her dressing room, and screamed for Swayne (or Nelson, as the case may be) who entered, looked at the rat, and said “That’s not one of mine!” According to Groucho, however, a year later that civilian rat had become the star of the act.
To find out more about the history of vaudeville, including animal acts like Swayne’s Rats and Cats, consult No Applause, Just Throw Money: The Book That Made Vaudeville Famous, available at Amazon, Barnes and Noble, and many other fine establishments.