While starring in The Dick Van Dyke Show (1961), Van Dyke called up Stan Laurel to ask for permission to do a Laurel & Hardy bit in an episode. Laurel told him that neither he nor Hardy's heirs owned the rights to the characters. Van Dyke and Reiner were horrified that Laurel didn't even own the rights to his own face, and this picture is the result.
In his autobiography, Carl Reiner said he intended this as a vehicle for Dick Van Dyke who had, on the set of their TV show, often expressed the wish that he had been working at the same time as comedy legends such as his hero Stan Laurel.
Writers Carl Reiner and Aaron Ruben wrote the story loosely based on the career of Buster Keaton - primarily the decline of his fortunes as tastes changed in Hollywood and his alcoholism. Some elements of the lives of Harold Lloyd and Mickey Rooney were also incorporated into this film.
The clip of the fictional Billy Bright comedy "Dr. Jerk and Mr. Hyde" is a parody of John Barrymore's 1920 silent film version of "Dr. Jekyll and Mr. Hyde." Like Barrymore, Dick Van Dyke (playing Billy Bright) transforms from Jekyll to Hyde on camera using only his facial expressions, and his ability to quickly switch from one to the other becomes the key gag of the scene.
In fact, the on-camera transformation was a bit more complex than that - Barrymore's makeup was done in tinted colours, and his costumes had coloured chalk applied to them. In the scenes that featured the transformation, the lighting colour was gradually changed, which, with the orthochromatic B&W film stock in use at the time (sensitive to only blue/green light, not to red) caused "Jekyll's" respectable clothing to appear to become "Hyde's" shabby suit, and to cause Barrymore's face to appear to change shape and contours. (Ortho stock will render pure red as black or dark grey)
In fact, the on-camera transformation was a bit more complex than that - Barrymore's makeup was done in tinted colours, and his costumes had coloured chalk applied to them. In the scenes that featured the transformation, the lighting colour was gradually changed, which, with the orthochromatic B&W film stock in use at the time (sensitive to only blue/green light, not to red) caused "Jekyll's" respectable clothing to appear to become "Hyde's" shabby suit, and to cause Barrymore's face to appear to change shape and contours. (Ortho stock will render pure red as black or dark grey)
Mickey Rooney wore a special prosthetic in his right eye to play Cockeye. The character was originally supposed to be cross-eyed, but on the first day of shooting the actor claimed he was physically unable to do this. Director Carl Reiner confirmed this by placing his finger on the tip of Rooney's nose and telling him to look at it, without result. Reiner later said about Rooney, "This man could do everything in show business - sing, dance, act - but he couldn't cross his eyes!"