The XD in the title comes from the classic text emoticon for a laughing face, with closed eyes and a wide open mouth, which became shorthand online for finding something extremely funny. Sounds built around that idea are shared widely as short reaction clips because they need no language or explanation to land. In memes, streams and short videos, a burst of exaggerated laughter like this works as an instant signal that something was meant to be funny, even when the joke itself is absurd or barely makes sense.