Well "hairy" means awesome, as well as "zero cool". So that makes it twice as cool! And "sweetness" inhances it even more! As for "fes"... I have no clue where that came from =P I didn't make that part up! So you put it all together, and it's this totally AMAZING, ROCKING word!!!!!!!!!!!
Used as an expression when someone does something so randomly stupid its funny. its sort of like, the action is the word after the "u know ur cool when" so "u know when ur cool when (you've peed in a can)"