This is the first half of a Marx Brothers double feature (with the other movie on the other side of the DVD). At the Circus is notable for Groucho's musical number "Lydia, the Tattooed Lady". Harpo also has a harp number, Chico a piano ditty. There is a love interest between the circus manager and a performer who (for some inexplicable reason) sings with a horse, and they're both awful. Eve Arden plays one of the baddies who want to take over the circus. She's only noticeable because, well, she's Eve Arden. Margaret Dumont is in the house, perhaps playing her role a little bit looser than in the other movies. Spoiler: she gets shot out of a cannon; I think that's probably the high point.
The laughs are there, but they're few and far between. Groucho doesn't even show up until ten minutes into the movie. Best you stick with their earlier stuff.