This is a practically plot less promotional short film from MGM. Like many of their shorts of the day, this one's in color as the studio was practicing how to use this before committing it to full- length films, as it was a very expensive process. They made several shorts like this...shorts with very little in the way of plot and a variety of stars either in the audience or participating as performers.
In this case, it's a bizarre circus with some characters wearing giant cartoon heads of famous movie stars of the day. As the acts are going on, you see mostly B and C-list stars like the Ritz Brothers, Olson and Johnson, Ben Turpin, Cliff Edwards and Leo Carillo. Some A-list or soon to be A-list stars (Boris Karloff and Alice Faye) are also on hand. Lee Tracy is on hand as the emcee. The entire list of the stars is listed on IMDb.
The film is a strange collection of acts and a really weird finale featuring Olson, Johnson and Mickey Rooney....which you just have to see to believe! Overall, diverting...but pointless.