Place it at the end of a reveal sequence, after the setup has made the secret obvious. Put It Was At This Moment He Knew just before it to frame the realisation, then follow it with Bruh Meme for a deadpan reaction to the confession.
Über diesen Sound
This 7.7-second voice clip repeats the word 'Merman' with growing excitement, turning a simple identification into a sudden, over-the-top announcement. It feels funny and surprising, like catching someone in a secret they can no longer hide, and it works because the delivery keeps building instead of settling.