What did you say???

Last weekend, the boy said "fart on me" when he passed gas. He happened to be with my parents and the time, so my mother says to him incredulously - what did you say and then he repeats it for her like it's what he's supposed to say. She then begins the interrogation- that is not nice to say that, who taught you how to say that, etc. The boy tells him Pawpi (my father) says that. My mom finally puts it all together and tells him, no, Pawpi says "pardon me". The boy simply responds 'oh'.