Perfectly Acceptable Excuses for Rude Behavior: Cocktail eavesdropping

The strangers' conversation you are not a part of must not be interrupted by you.

But should you choose to ignore this Absolute Truth (as pluff-mudders at cocktail parties often do), here are some excuses:

"I couldn't help but overhear. It's part of my training. I am Special Agent Haltney Trapp III of the FBI, and you might be the Most Wanted Person I've been tracking."

"I'm from Bhutan. May I practice my English with you nice people?"

"I'm trying to make new friends. Want to go for coffee?"