Early in the movie, the Marx Brothers - playing stowaways concealed in barrels - harmonize unseen while performing the popular song 'Sweet Adeline.' It is debated whether Harpo was actually singing or not.
Groucho's line "Gary Cooper is much taller than me." becomes "Charlton Heston is much taller than me." in the Spanish dubbed version. Heston was only 7 years old when "Monkey Business" was released.
One of over 700 Paramount Productions, filmed between 1929 and 1949, which were sold to MCA/Universal in 1958 for television distribution, and have been owned and controlled by Universal ever since.
In the movie, Groucho Marx tells Thelma Todd, "You're a woman who's been getting nothing but dirty breaks. Well, we can clean and tighten your brakes, but you'll have to stay in the garage all night." Four years after making this movie, Thelma Todd died under mysterious circumstances. She was found dead in her car inside her backyard garage with the engine running. It is not known if her death from carbon monoxide poisoning was accidental, a murder, or suicide.
According to Robert Osbourne, during the first day of shooting, it's reported that the Brothers Marx showed up in each other's clothing and impersonated each other.