Ganbatte is a common Japanese encouragement meaning do your best, while onii-chan is an affectionate way to address an older brother that became a staple phrase in anime and otaku culture online. Clips pairing the two spread on soundboards and in edits alongside other cute catchphrases like Tuturu, and as a standalone onii-chan call used for teasing or support. Because the exact source recording is not documented, its popularity comes from repeated use in memes, streams and fan videos rather than one specific series, keeping it as a generic wholesome anime cheer.