Wario is Mario's greedy, mischievous rival, a character who has appeared across Nintendo's Mario games since the early 1990s, and his loud Yahoo is one of his signature celebratory shouts. In Super Mario Maker, short character sounds like this became easy to lift, clip and reuse, and the taunt spread through gameplay videos, edits and meme compilations where a boastful reaction was needed. It remains popular because it is instantly recognisable, very short and carries a complete attitude in under a second, making it a quick shorthand for victory, greed and playful gloating.