It's from the movie he starred in called Patch Adams where he did what he always did off of the big screen. He made people smile. He took the time out of his life, pushed his hurt aside and just made other people happy.
Well for one, the filly's cutie mark is a magic lamp, most likely referencing the Genie from Disney's Aladdin. The picture itself I believe references a movie Robin Williams was in, but I don't know which one it was.
Don't quite know what to think of this. Great tribute on the surface, but Patch Adams isn't a good movie at all and the liberties hollywood took with it make me wonder if Robin Williams regretted working in it. Especially since the studio never even helped the real Patch Adams with anything more than a fundraising set up. Good luck with that when the movie meant to spread the message is a horribly cut throat selling scheme amidst just being horrible.
Hate to reign in the moment, but I despise how shallow of a statement "laughter is the best medicine" can be, with or with out the help of the entertainment industry.
Sorry PixelKitties, I know you want to pay tribute to someone who gave to you, but that movie and everything behind it is a completely disrespectful mess.
P.S. I do have a substitute solution if you're interested, you can pretty much keep a lot of the picture in tact.