"It's a happy song!" ... "It's a sad song!!!!" Happens everytime. My 78yo mom loves to show this song to everyone, she was at this Festival da Canção's audience when Gilberto Gil and Os Mutantes played this, and she's right now laughing hard at your face, because at the "beware the knife!" line, everyone did have the exact same reaction as you. "Including myself!", she's telling me. Boggling eyes everywhere.