Groucho Marx as Dr. Hugo Z. Hackenbush

Chico Marx as Tony

Harpo Marx as Stuffy

Allan Jones as Gil Stewart

Maureen O'Sullivan as Judy Standish

Margaret Dumont as Emily Upjohn

Sig Ruman as Dr. Leopold X. Steinberg

Leonard Ceeley as Whitmore

Douglass Dumbrille as Morgan

Esther Muir as 'Flo' Marlowe

Robert Middlemass as Sheriff

Vivien Fay as Specialty Dancer

Ivie Anderson as Specialty Singer

Gino Corrado as Man Boarding Bus (uncredited)

Bess Flowers as Racetrack Spectator (uncredited)

Bert Moorhouse as Racetrack Spectator (uncredited)

Frank O'Connor as Racetrack Guard (uncredited)

Carole Landis as Party Guest (uncredited)

Etta Moten as Black Singer (uncredited)

Dorothy Dandridge as Singer (uncredited)

Byron Foulger as Racetrack Spectator (uncredited)