The phrase comes from SpongeBob SquarePants, where the narrator reads out time cards between scenes to signal how much time has passed in Bikini Bottom. One eternity later became a fan favourite because it takes that familiar format to an absurd extreme. Clips of the line spread through YouTube edits, reaction videos and TikTok, where creators reuse it as instant shorthand for a long wait, a delayed payoff or a slow transformation. Its staying power comes from that instant recognition: even without seeing SpongeBob, listeners know a ridiculous amount of time is supposed to have passed.