Place it right after the mistake is revealed, as the character's reaction beat, then follow with Ba Dum Tss to close the joke. For a bigger build-up, open with Drama before the slip, let this clip answer it, and keep the sequence short so the reaction stays the focus.
Sobre este som
This is a very short, high-pitched voice clip of about one second, built around a single flustered hawawawa exclamation delivered in an exaggerated anime style. It feels like a sudden cute meltdown, full of panic, confusion and embarrassment, as if a character has just been caught out and is scrambling for words. It lands instantly and makes an awkward slip feel playful rather than serious.