Robin Williams agreed to be the Genie for Aladdin under the condition that his voice would not be used to sell merchandise. Disney did not hold up their end of the deal, overdubbed his voice for advertisements, then sent him a Picasso painting as an apology.
Ron Clements, co-director of Aladdin, confirmed the fan theory that the merchant at the beginning of the film is actually Genie. “[we] had that at the end of the movie, where he would reveal himself to be the Genie… [through] editing, we lost the reveal at the end. So, that’s an urban legend that actually is true.”