The phrase means oh, how nice in Portuguese, and this clip is shared mainly as a short sarcasm reaction rather than as a line tied to a specific film, show or celebrity. Its popularity comes from how easily the tone translates even for listeners who do not speak Portuguese, because the stretched vowel and flat delivery signal irony on their own. On soundboards and in short-form videos it circulates alongside other mocking reaction sounds, used whenever a creator wants to pretend to be impressed while making clear they are not.
About this sound
A sarcastic Portuguese voice drawls ooohh que legal, turning a fake compliment into a mocking reaction. It fits fake praise and unimpressed reactions in memes.
The clip is a single drawn-out voice saying ooohh que legal, the Portuguese equivalent of oh, how nice, but delivered with a slow, flat, exaggerated tone that makes the praise sound completely insincere. The stretched ooohh rises and then falls, while legal lands with a knowing, almost bored emphasis, so the listener instantly understands that the speaker is not impressed at all. That gap between the polite words and the mocking delivery is what makes it funny, turning a simple compliment into a sarcastic jab that works best when the on-screen moment is disappointing, obvious or painfully overhyped.