We're not sure exactly how to transform your video-playing Apple TV into an emulation station just yet, but we do know that there's an awful lot of Apple TV hacking going on and the above video purports to show a very functional copy of Super Mario Bros. running off the tiny little box.
AwkwardTV has a page set up listing some emulators that work with the Apple TV writing, "These emulators are being tested with standard ROM's on the AppleTV running the original OS except for being slightly modified to add SSH." Is anyone tired enough of waiting for Apple's inevitable game offerings to upgrade their Apple TV themself?