A character thinks he can speak some language, but fails comedically and says something entirely different than what was intended -- often complete nonsense or something rude. For example, maybe he tries to say "Can I please buy some matches?", but actually says "My Hovercraft Is Full Of Eels". Hilarity Ensues. A common explanation for the trope is that the character making the mistake has been taught something rude by a mischievous native speaker, playing on their ignorance to purposefully give an obscene translation for something reasonable. Not to be confused with I Need to Go Iron My Dog.