This sound comes from Minecraft, the sandbox game first released by Mojang in 2011. Short in-game effects like this became popular in memes and editing because they are instantly familiar to players and easy to place on quick visual gags. The egg plop sound is often used when something small, harmless or mildly disappointing happens on screen. Its staying power comes from Minecraft's huge online culture, where even tiny gameplay sounds are recognizable enough to become reaction cues in shorts, compilations and stream edits.