back in five - minutes
what's up? - it's a direction, but that's not important right now (Airplane)
not the brightest crayon in the box - not too intelligent, not the sharpest tool in the shed, elevator doesn't go all the way to the top, a few bricks shy of a load, a few items short of a taco plate (you get the picture. I feel like I'm channeling George Carlin...
Think outside the box - approach a problem from a non-traditional way. Consider it as if you've never thought about it. Try new approaches, etc.
Phat - a slang term, meaning high-quality, worth having, etc. This stuff changes just as soon as a non-'in crowd' person reports it.
Shorty - a woman. why, I dunno...
how ya doin' - actually a noise that means 'I recognize your presence, but do not necessarily want to engage in conversation' - see also 'what's up', how's it hanging, whazzup, etc.
the one that always had me scratching my head was a real old one.
-I love my wife but oh you kid -
ok, do you love your wife, but you're tempted, or you love your wife, but not seriously?...