Put it at the end of a short fail clip, just after the mistake is visible, then follow it with a game show buzzer for a second comic beat before cutting to the next scene. For a longer goofy sequence, open with goofy ahh sounds and save this honk for the final punchline.
About this sound
This is a short, squeaky honk lasting about three seconds, with a rubbery, high-pitched squeeze that sounds like a clown's bulb horn. It feels instantly silly and deliberately over the top, turning a clumsy moment into a joke. The sharp comic squeak makes embarrassment feel playful rather than harsh, so a fail lands as light slapstick instead of a real mistake.