Robin Williams was a big, big gamer. I've read stories on how he would play games with Steven Spielberg online, and of course his daughter is named Zelda. His passing was a pretty big shock, but Blizzard is going to pay tribute to great actor and comedian.
Testers in World of Warcraft: Warlords of Draenor have found a few references to the late actor. First, a genie was found which recites one of his famous lines from the movie Aladdin. Another area has a broken egg with a character dressed like Mork. Finally, another NPC was found dressed like Mrs. Doubtfire. You can see more at WowHead.
I think this is great that Blizzard has gone and added these little finds for players of World of Warcraft and I bet Robin would've loved it as well.