Mario is Nintendo's mascot from the Super Mario platform games, first appearing in the 1980s and becoming one of the most recognised voices in gaming. Short voice clips of the character have circulated for years on soundboards and in meme edits, where his expressive delivery is repurposed far outside the games. This what are you doing line follows that pattern, used online as a standalone reaction to call out strange behaviour. Its popularity comes from instant recognition and the contrast between a friendly hero and an accusatory question.