Put it at the end of a build-up, after Sudden Suspense has raised the stakes, so it lands as the verdict on a bad idea. Follow it straight away with Nelson's Ha-Ha! to keep the mockery going, then cut to the reaction shot before the joke cools.
Über diesen Sound
This is a short 2.6-second voice clip of Sssniperwolf saying, 'Nah, that's the Joker,' in a flat, dismissive tone. It lands as amused disbelief, the kind of quick reaction you give when someone's idea is so chaotic it only makes sense coming from the Joker himself.