Have we learned something today? I learned that your as dumb as a post!
"I'm five years old, mom, you should know that!"
Can also be used to describe a boyfriend/girlfriend that you're using to pass the time until a good one comes along.
Walter: Nah man, this place is always full of fives!
Lloyd: Yeah, I've really been thinking about getting serious with my chic dude...
Walter: What?! You know that chics just a 5 man, even you can do better.