“This is big brain time” became a widely shared internet reaction sound through meme edits, short clips and reposts across social platforms in the late 2010s. The phrase is used to label moments of supposed genius, whether the idea is actually smart or obviously foolish. Its staying power comes from how quickly it communicates “high IQ” sarcasm in under two seconds. In meme culture, it often fills the same role as a bruh reaction or a buzzer, depending on whether the joke is praise or mockery.