List of references on the Internet

Homestar Runner
On homestarrunner.com, there is a toon called "Pumpkin Carve-nival". In it, The King of Town is dressed as Mario. When the toon is over, click on him to unlock a secret minigame: "Super Kingio Bros."

Also, in the toon "Halloween Potion-ma-jig" The Cheat is dressed as Toad.

In the toon "Teen Girl Squad Issue 10" the character Tompkins is apparently playing a Mario game on an old Game Boy. Tompkins says he "has Bowser on the ropes" and a Koopa shell "pÃ˜wn"s So and So. Later on, the Ugly One says "Lets get it on like Diddy Kong".

The game "Stinkoman 20X6" features its very own version of the Minus World, Level -0, "NEGATORY". Unlike the Minus World, it is beatable (as well as part of the game), but is far glitchier than Minus World.

Kingdom of Loathing
KingdomOfLoathing.com is a text based RPG-type game, where you create a character out of the wacky classes they have available, then level up in a world where anything goes. In the Kingdom of Loathing there is a zone called the "8-Bit Realm," where there are various enemies from the NES-era for you to kill, including Bob-ombs, Koopa Troopas, and Goombas.

There are also various items you can buy throughout the Kingdom of Loathing that are Mario-esque in name, description, and use.