http://www.urbandictionary.com/define.php?term=g-pants:

Short for genius-pants or gangster-pants. A nickname for an awesome, funny, sweet, clever, all-rounded person who is willing to help you with anything. Comes first in everything, but their achievements can sometimes get to their head & their ego is sky high. Nonetheless, very awesome.

Hey, g-pants! You're awesome!

А еще это марка подгузников...