Comment by godzillabrennus

Here's something i didn't know:

[producer and director] had written the role of the Genie for Robin Williams, but when met with resistance, created a reel of a Williams's stand-up animation of the Genie.

The directors asked Eric Goldberg, the Genie's supervising animator, to animate the character over one of Williams's old stand-up comedy routines to pitch the idea to the actor. The resulting test, in which Williams's stand-up about schizophrenia was translated to the Genie growing another head to argue with himself, made Williams "laugh his ass off", and convinced him to sign for the role.

Williams's appearance in Aladdin marked the beginning of a transition in animation to use celebrity voice actors rather than specifically trained voice actors