From 1989 through 2003, Robin Williams took center stage in Walt Disney World's Magic of Disney Animation tour at Disney's MGM Studios (now Disney's Hollywood Studios). Williams starred in Back to Neverland, a 10-minute film that was part of the tour, alongside Walter Kronkite. Williams played a tourist who gets turned into a cartoon by a Disney animator, who draws him into sets and lets him interact with characters from Peter Pan.

Back To Neverland: Walter and Robin from Joe Pitt on Vimeo.

Also, if you haven't seen it, this tribute to Williams created by Disney animators is pretty amazing:

The text reads: "We’re deeply saddened by the loss of Robin Williams, a wonderfully gifted man who touched our hearts and never failed to make us laugh.  An incredible actor and a comedic genius, Robin will always be remembered for bringing some of the world’s favorite characters to life, from his zany alien on ABC's Mork & Mindy to the irascible genie in Disney's Aladdin.  He was a true Disney Legend, a beloved member of our family, and he will be sorely missed.  We join Robin’s friends and fans everywhere in mourning, and offer our thoughts and condolences to his family during this difficult time. – Robert A. Iger, chairman and chief executive officer, The Walt Disney Company