While John Wayne holds the record in "The Guinness Book of World Records" for playing the most leading roles, Mickey Rooney has appeared in more than 300 films. As of March 2014, Rooney also has a number of TV credits to his name.
The question of who appears in the most films becomes more unclear considering specialties like short films and voice work. For instance, Mel Blanc, the voice behind Bugs Bunny, has more than 1,000 credits to his name, but many of these credits include television work and animated shorts. Stunt performers also tend to have more credits than actors on screen.