Regular Show episode Fortune Cookie
January 23, 2012
In the thirteenth episode of season 3 (Episode #53), Rigby is seen playing a video game called Super Donkey Bros. While the name is a reference to Super Mario Bros. (and possibly Donkey Kong), the game actually plays like Pong, with the paddles replaced by donkeys.
Super Donkey Bros. is shown again in "JoySpot Arcade" in the episode Busted Cart.
The creators of Regular Show didn't hold any right over Nintendo's Mario, but they only included a minor reference to the series.