The Joker has been one of pop culture's most recognisable villains for decades, and a shush from him carries an instant sense of mischief and control. Online, short clips of that gesture are reused in memes, reaction videos and edits whenever a creator wants to stop a conversation cold or signal that something secret is about to happen. Because the sound is only about two seconds long, it fits easily into short-form video, where a quick, recognisable cue can set the tone before the punchline.