The punchline to an old joke which was cited in the movies "The Sting" by an anonymous comedian and, more recently, in "Men in Black" by Tommy Lee Jones.
After hearing that punchline twice, I went to my old pal Google to find out the rest of the joke. It goes something like this:
An old guy approaches the window of the movie theater with a chicken on his shoulder, and asks for two tickets. The girl at the counter wants to know who is going in with him. He replies, "Well, my pet chicken, of course!"
The girl tells him that he can't take a chicken into the theater, so he goes around the corner, and stuffs the chicken into his pants. He returns to the window, buys his ticket and goes in.
Inside the theater, the chicken starts to get hot and begins to squirm, so the man unzips his pants so the chicken can stick its head out and watch the movie.
Sitting next to him are two old women. The one closest to the old guy nudges her companion and whispers, "Lucy, this man over here has just unzipped his pants!"
Her companion whispers back, "Oh, don't worry about it. If you've seen one, you've seen them all."
"I know, but this one's eating my popcorn!!"