Mario is the official Mascot to Nintendo and the main character of the Mario series.
Relevance to Rare
He makes an appearance in Donkey Kong 64 in the Donkey Kong arcade game in Frantic Factory. There was a few other cameos of him in other Donkey Kong games. In Donkey Kong Country 2: Diddy's Kong Quest and Donkey Kong Land 2, Mario is ranked first place on Cranky Kong's Top 3 video game characters unless Diddy and Dixie Kong collect all of the DK Coins.
Mario appears in the DS game, Banjo and Kazooie: Life of crime. He is the game's final boss. However, due to the game being banned, he didn't appear.