to make a fool of oneself, to embarrass oneself
Escorreguei em uma casca de banana e todo mundo viu, paguei muito mico!
I slipped on a banana peel and everyone saw it, I made a fool of myself!
'Mico' in Brazilian Portuguese is a small capuchin monkey, and 'pagar mico' became popular 1990s slang — probably from the card game Mico in which the player left holding the 'mico' card at the end of the round loses.
Source: Superinteressante — Pagar mico.
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