If you're in the middle of a game of Counter-Strike: Global Offensive and suddenly get the urge to play Super Mario Bros., there are a few options open to you. You could stop playing CS: GO. You could grab a nearby 3DS, perhaps yanking it from the hands of a passing four year-old, and balance it under your monitor, using a series of elaborate poking devices to manipulate the game. Or you could join Reflex Gamers' CS: GO server, where they've created an emulated SNES within cs_office, complete with controllers and cartridges. You have to see this.
Though the game is an obvious clone of Nintendo's plumber sim, they've smartly called it “Super Mareo Bruhs” and it runs on the "Sourcemod Entertainment System", also known as the "SMES". Take that, Nintendo's in-house search engine lawyer team. You'll never find it. It's seriously impressive, and the console it's played on is fully animated, too. The buttons click!
The only problem I've found is it imbalances the game: while the Counter-Terrorists swarm over the office, hunting the bad men and looking super-cool and dashing, the Terrorists will be gathered around the console, jostling for a shot at the crude platformer. There could be a fun mode here: the Terrorists have to protect the player on the console, and at the end of the rounds they team with the highest score in the SMES game wins.
Kisses to Ars Technica for finding it.