Joke about Bulldog + Shi*tzu cross breed

The scene I which one of the characters says to the mother "Hey mum did you know there is a now a bulldog-Shi*tzu cross breed. It's called a Bull Shi*tz". Let me tell you, I made that joke up long before it appeared in this film. Unfortunately I will never be able to prove this at all, But I swear to God it's the truth. So when the mother replied "That's very good Mark, did you make that up yourself?", I yelled at the TV screen and said "No he didn't make it up, I did"