The Simpsons episode Marge Be Not Proud
December 17, 1995
In the eleventh episode of season 7 (Episode 139), Bart wants the new extremely violent video game Bonestorm, but is having trouble getting it. After Jimbo and Nelson brag to him about their shoplifting, Bart observes that the display case housing Bonestorm has been left open. As he contemplates stealing the game, some video game characters pop up in his mind and talk to him, with Mario and Luigi among them:
- Luigi: Go ahead-a, Bart, take-a the Bonestorm.
- Mario: The store, she's so rich. She'll-a never notice.
- Donkey Kong: Duh, it's the company's fault for making you want it so much.
- Lee Carvallo (a character based on Lee Trevino): Don't do it, son. How's that game going to help your putting?
- Sonic The Hedgehog: Just take it! Take it, take it, take it, take it, take it. Take it!
In this cameo Mario and Luigi's heights seem to be switched, but it's also possible that are their colors to actually be switched, since the green one appears first.
Note that even if they directly talk to Bart, this is not considered an in-universe link, but just a sub-universe link, since they are still just fictional characters within the Simpsons' universe.
The Simpsons episode The Father, the Son and the Holy Guest Star
May 15, 2005
At the beginning of the twenty-first episode of Season 16 (Episode 356), when Principal Skinner is introducing the school play, he says, "Now kids, since the Middle Ages had no compact discs or Super Mario Men..."
The Simpsons Comic issue #110: Bad News Bearer
The story revolves around Ned Flanders becoming video game addicted and eventually becoming uncouncious from playing too much. In the end, after recovering, he says he'll make a mushroom pizza, but then sees a Toad-like being appearing next to him. He then starts chasing him appearing dressed as Luigi and the Simpsons family is shown as video game characters too, with Bart as Mario, Homer as Donkey Kong, Lisa as Sonic the Hedgehog and Marge as Lara Croft.
The Simpsons episode Please Homer, Don't Hammer 'Em
September 24, 2006
In the third episode of Season 18 (Episode 381), Marge gets a job as a carpenter, but has Homer posing as the one working since men won't accept carpenter work made by a woman.
When they are in their carpentry clothing, Marge wears overalls and a green shirt while Homer wears overalls and a red shirt, the respective colors of Luigi and Mario.
However is possible for this to be just a coincidence.
The Simpsons Comic Issue #130: Marge the Sellout
Marge gets into the habit of auctioning off all of the family's possessions online. She soon auctions off Bart's old video games to the chef character Luigi Risotto. After Luigi wins the auction, the next panel reveals that he has a brother; a plumber who's dressed up like Mario. The "Mario" character asks Luigi to help him fix a leaky pipe, to which Luigi responds "Hold your mushrooms! I'm-a coming!".
The Simpsons Game
October 30, 2007
The level "Enter the Cheatrix" takes place inside a game factory and characters looking like Mario and some Koopa Troopas can be seen working behind windows while Warp Pipes similar to those from the Mario series can be used by the player to travel around and making noises similar to the original ones while used. The ending clip of the level also reveals Frink having a turtle similar to a Koopa Troopa as wife. A Mario-like character also appears in the introduction clip of the last level of the game, called "Game Over" and speaks similarly to Mario after Homer asks what's for dinner, saying "I hope it's-a spaghetti! Here we go!"
The Simpsons episode O Brother, Where Bart Thou?
December 13, 2009
In the eighth episode of Season 21 (Episode 449), Bart complains about not having a brother and in a scene he dreams many famous brothers including the Mario Bros., seen jump into a pipe, hit a block and chase after the mushroom that pops out of it.
The Simpsons episode A Totally Fun Thing That Bart Will Never Do Again
April 29, 2012
In the nineteenth episode of Season 23 (overall episode 505), One of the activities listed on the schedule for the cruise ship is "Human Super-Mario Brothers". Whatever it is it lasts 55 minutes, since it's from 8:05 to 9:00.
The Simpson's company FOX doesn't own any right over Nintendo's Mario characters, so they were only able to do subtle references, citing the games as fictional or making slightly modified versions of the characters appear.