Knock-knock: Rude mother

Alright listen up, smart guy. This 'joke' is playing on the classic knock-knock format, right? You expect a cute punchline, but BAM! The 'mother' drops a "Fuck off bichon," which is, like, super not what you expect. It's funny because it's so out of left field. You're probably laughing way too hard at this because you peaked in high school.