The line comes from the Portuguese language dub of Shrek, the DreamWorks animated franchise that began in 2001 and made Donkey one of its most quoted characters. In Portuguese burros means donkeys, so the phrase plays directly on Donkey's role and on the everyday use of burro as an insult for a foolish person. Short dubbed film lines like this spread widely on Brazilian and Portuguese soundboards and in meme edits, where the familiar movie voice makes an ordinary insult instantly recognisable even out of context.