Place this clip under the thinking pose at the start of the scene, then follow it with the bruh sound effect once the underwhelming idea is spoken, and save any reaction shout for after that reveal.
About this sound
This clip is the dorime chant section from a choral vocal performance, with layered voices singing Latin-sounding syllables for about eleven seconds. It feels solemn and grandiose, which makes a small, obvious thought seem hilariously inflated and self-important. It comes from Ameno, the 1996 song by the French new-age project Era.