Scrappy is running a sideshow, as you might guess from the title, and Margie, the little girl who has appeared in some other episodes of the series wants to come in. She sneaks in and accidentally sabotages some of the acts, particularly those starring Scrappy.
Some of the gags are old but good ones, like the fake strongman bit, and some are possible only in a cartoon, but they come in sufficient number and variety to make up for the deficiencies in any single one,