At the theatrical opening of this film, kids were handed (for free) an "autographed" picture of Rhubarb. The signature on the photo was a paw print.
The book, "Rhubarb" was published in 1946. In it, Yeager takes his boss, Banner to the movies, to a domestic comedy. Banner doesn't like the leading man, because he saw him play a drunk in another movie. Clearly they are referring to Ray Milland in "Lost Weekend". Five years later, Ray Milland plays Yeager in Rhubarb, le chat millionnaire (1951).
Fourteen different cats portrayed Rhubarb at various points in the film. Each cat was trained to do a specific trick. Three of the most identical cats appeared in the courtroom scene where Polly Sickles has to choose which one is the real Rhubarb.
The baseball park called "Banner Field" in the movie is the real-life Wrigley Field in Los Angeles.
Paul Douglas: At the end of the movie, sitting on a park bench and looks at the cat and kittens as they go past and says 'What a cat - a litter to three wives...", a reference to his film Chaînes conjugales (1949). Douglas was married to star Jan Sterling at the time.