Team Fortress 2 is Valve's class-based multiplayer shooter first released in 2007, and the Pyro is its flame-wielding class known for speaking only in muffled mumbles through a gas mask. The game uses short character voice responses for actions like capturing, healing and helping teammates, which players have clipped for years. This thank you line became a staple reaction among fans because the emotion is clear even when the words are not, and it now circulates widely in edits, streams and soundboards as a quick TF2 reference.