Batman - Best Friends Forever

Edit~ In retrospect I really should have run this by a few more friends to see if they got the joke... so I added one more panel I hope it helps! x_____x;

HOLD IT! I know you're about to run off to Youtube to listen to a certain, unforgettable tune. No need; I've generously provided you a link right here! [link] Hehehehehehe!

Though if you don't get what I was referencing at end I messed up a perfectly good Batman joke... :/ I was originally going to put Mario in the fourth panel but I thought this punchline was much funnier.

I'm playing Arkham City, can you guess? XD I don't get why Penguin and Freeze aren't totally chill with each other, they should be best friends!