The Marx Brothers burst onto the scene in the 1929 comedy "The Cocoanuts". Over the next few years they starred in some of the all-time classics, namely "Horse Feathers" and "Duck Soup".
Then something happened. I don't know the reason, but they left Paramount (which financed the aforementioned movies) and moved to MGM. By that point, MGM was well established as the domain of happy-go-lucky musicals, and it showed in the Marx Brothers' movies. Far from the biting satire of their earlier movies, these newer movies tended to show them performing antics in various settings: opera, horse racing, and now the circus. "At the Circus" is funny, but it's no "Duck Soup".
Ignoring all that, there's plenty of laughs to be had here (and quite a few hot babes). Enjoyable in that respect. Jerry Maren (Atom) is best known as one of the Munchkins in "The Wizard of Oz" and died only last year, making him not only the last surviving speaking cast member from TWoO, but the last surviving cast member from a Marx Brothers movie.