This sound is mainly shared online as a short hype cue rather than for a widely documented film or TV origin. In meme edits, short-form videos and reaction posts, people use “Yahoo, showtime” to announce that something big, ridiculous or entertaining is about to happen. Its staying power comes from how fast and readable it is: the phrase instantly sets expectations, then gets out of the way so the visual joke can land. That makes it a reliable setup sound for fast-paced internet editing.