Also applies to any situation where a person who is, in fact, a heterosexual cannot proceed to do something that they want without strongly suggesting otherwise.
Guy 1: So what's the deal with Tom? Is he gay or what?
Guy 2: I don't know...Its hard to tell.
Guy 1: I guess one of us could go over there and try to make-out with him, but its a catch 69.
Guy 1: Hey, straight guys can wear skinny jeans, right?
Guy 2: Well sure straight guys can wear skinny jeans...its just that those guys tend to engage in sex with other men...
2) This has also been used to reference an eyebrow ring getting caught in pubic hair.
3) Pubic hair caught in one's teeth after engaging in a 69.
2) "Sorry sir, but I can't hire you on account of your eyebrow ring."
"You said piercings were fine!"
"Not when they have public hair in them."
3) "You have something in your teeth."
"Is it salad?"
"Only the thoroughly tossed variety."