Other mistake: When Harpo and Chico are shooting spitwads at Groucho in the classroom, Groucho's line gets cut short when he is hit flat on the side of the head with a book. He then falls back and says, "You got me" and if you listen closely you can hear someone laugh in the background.
Horse Feathers (1932)
1 other mistake
Directed by: Norman Z. McLeod
Starring: Chico Marx, Groucho Marx, Harpo Marx, The Marx Brothers
Continuity mistake: Groucho plays 'Everyone Says I Love You' in a boat, and he is playing a solid-body acoustic/electric guitar. At the end of the song, he throws the guitar into the pond, but it has become a regular hollow-body acoustic.
Professor Wagstaff: Oh, I love sitting on your lap. I could sit here all day if you didn't stand up.