Actor Michael Keaton is hobbling around on crutches after breaking his foot in a mystery accident.

The former Batman star revealed his injury during an appearance on David Letterman's Late Show on Friday (24Apr09).

Keaton refused to reveal the real cause of the break, just saying, "I don't want to make a big deal about it. I broke my foot."

Instead the pair pretended he had hurt himself rescuing kids from a fire. Letterman screened a fake newscast by broadcaster Anderson Cooper, that claimed: "Michael Keaton broke his foot rescuing twelve children from a burning orphanage."