Jimmy Kimmel in 2007
We wanted to figure out a way to get crank phone calls on television. Watching someone on TV talking on a phone isn't that entertaining, and obviously we couldn't send a camera crew around to the people getting the calls, so it was limited to either animation or puppets. And puppets seemed halfway between cartoons and people, so that seemed like the most real way that we could do it.
Jimmy Kimmel, 2002

Source

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Hart, Hugh (May 30, 2002). "Kimmel, Carolla Pulling The Strings On Crank Calls Show". South Florida Sun-Sentinel. p. 3E.