The tabloid-version of a TV-movie, chronicling the often-annoying off-screen antics of Robin Williams (Chris Diamantopoulos) during the ABC sitcom's run from 1978 to '82. Pam Dawber: Erinn Hayes. Garry Marshall: Daniel Roebuck. Valerie: Michelle Harrison. John Belushi: Tyler Labine. Ron Howard: Shaw Madson. Henry Winkler: David Josefsberg.