....and then the duck said to the barman "just put it on my bill"
That punchline is my go-to for when you're talking about someone and then that person comes into the room unexpectedly and you need to act like you were talking about something else. One time years ago there was a bunch of us getting high in someone's living room and I was talking in a less than flattering way about this person who walked in right as I was saying it, so I immediately launched into the duck/bill punchline and of course everyone broke out into hysterics at the situation. The subject stood laughing in the doorway saying "oh man that sounds like a good joke, what's the rest of it," which of course made everyone laugh even more, and all I could say was "Oh man it was really long, I'm not telling it again, perhaps some other time." For ages afterwards he kept asking me to tell him the whole joke and I had to change the subject
