The clapping comes from Work at a Pizza Place, the long-running Roblox roleplay game where players cook, deliver and serve pizzas and run the shop together. Sounds from the game get clipped and reused outside Roblox because they are short, clear and instantly tied to completing a task. This applause works the same way on video platforms, where creators use familiar game effects as quick reaction cues. It stays popular because a few seconds of clapping needs no explanation and fits both genuine celebrations and ironic, over-the-top praise.