Place it after the reveal beat in a reaction edit, before a cutaway reaction shot. Follow it with Nelson's Ha-Ha! Sound Button for a second laugh layer, or precede it with the Oh My God Wow button when surprise needs to land first.
Über diesen Sound
This is a 1.3-second burst of high-pitched giggling that spells itself out as hi hi hi, he he he, then ha ha ha ha, getting bigger as it goes. It feels gleefully wicked and a little unhinged, like a cartoon villain who just got away with something small and silly and cannot hold it in.