It's from the game Contact, which uses a certain (small) amount of intertoobz slang. This quote in particular is from the Professor, who sort of acts as a go-between between you, the player (whom he addresses directly) and the character you're controlling. He tends to hang out in the top screen, commenting occasionally on the stuff the character you control is doing in the bottom screen.

I thought only Fifthfiend said weaksauce. Fifth is a they?