Mr. Magoo's creation was a collaborative effort; animation director John Hubley is said to have partly based the character on his uncle Harry Woodruff, and W. C. Fields was another source of inspiration. It has also been said that Harvard professor Francis P. Magoun was the model for the character. The Magoo character was originally conceived as a mean-spirited McCarthy-like reactionary whose mumbling would include as much outrageous misanthropic ranting as the animators could get away with.
The voice of Mr. Magoo, Jim Backus, often told the tale of how he originally discovered Magoo's voice when he put on a fake rubber nose that pinched his nose slightly, giving it the nasal sound. He was only able to perform the voice with the help of the rubber nose for some time, but eventually learned how to re-create it without its assistance. He would usually pull out the nose (or a facsimile, since the original had been lost some years before) and put it on and break into the familiar voice.