Context

This line is spoken by Felix Unger (Tony Randall), in the TV show The Odd Couple (1970-1975).

When neat freak Felix Unger must defend his slobby roommate, Oscar (Jack Klugman), he has a tidy takedown for one witness who isn't quite sure exactly what she saw. She was only making an assumption, but after Unger's outstanding smackdown, we think she probably learned her lesson.

Where you've heard it

You've heard this any time someone makes an erroneous assumption. This is such a popular phrase, we'd be willing to bet you didn't know it came from a television show. Did you just assume it came from Shakespeare, or something? Well, we know what happens when you assume.

Pretentious Factor

If you were to drop this quote at a dinner party, would you get an in-unison "awww" or would everyone roll their eyes and never invite you back? Here it is, on a scale of 1-10.

It's pretentious to assume, but not to call someone out on it. And this line is just too sharp to be totally pretentious.