At the Circus (1939)

Worth it for one number: Groucho, as the lawyer J. Cheever Loophole, singing Harold Arlen and Yip Harburg's "Lydia, the Tattooed Lady," a comic song that became one of his signatures; he was still performing it at Carnegie Hall in 1972. Margaret Dumont is back as well, which always helps. Around those highlights is a fairly ordinary rescue-the-circus plot, with too much time spent on the young lovers and their songs. It marks the point where the MGM films start running on formula, so treat it as the first of the lesser pictures: enjoyable if you already love the team, thin if you don't.