World of Warcraft
November 23, 2004
World of Warcraft features two characters clearly based on Mario and Luigi, respectively called Larion and Muigin, having their initial letter swapped and a "n" added in the end. They weild giant hammers, just like Mario does in Donkey Kong and some other occasions.
Larion and Muigin can be found at Marshal's Refuge in the contested territory of Un'Goro Crater and give side quests to the players. In the Cataclysm expansion they can be found pacing in circles at the top of two guard towers in Marshal's Stand.
Additionally the game features an item called Red-speckled Mushroom, that is very likely a reference to mushrooms from the Mario series, since it not only is red with white spots on its cap, but is also shown in its icon as having two black spots on its stem, resembling eyes.
Once eaten this Mushroom heals 243 HP over 21 seconds. It can be bought from many shopkeepers throughout the game for 1s 25c, but it can also be looted from Undead monsters in level 9-23, and is a reward for completing the "Cave Mushrooms" quest, found in Barithras Moonshade.
Warcraft's company Blizzard had no right over Nintendo's characters, in fact they only included parodies of those characters.