The AIM incoming message sound comes from AOL Instant Messenger, the hugely popular desktop chat program that defined online messaging for many users in the late 1990s and 2000s. As AIM became part of everyday internet culture, its alert tone turned into a shorthand for instant messages, buddy lists and away-message nostalgia. The clip still shows up in memes, retro edits and comedy videos because a single beep immediately tells viewers that a message just arrived, even if the scene is not literally about AIM.