Place this clip over the main visual gag, then follow it with goofy ahh sounds for the reaction shot and a baby laughing button as the closer on the final frame.
このサウンドについて
An eight-second clip of a high-pitched, playful voice repeating “patito patito oniichan” over and over in a childish chant. It feels cute and deliberately absurd at the same time, turning even a straight-faced reaction or a tiny pet on screen into something gleefully unserious and hard to take seriously.