Comes from the French language, where 'yes' is said 'oui oui,' which sounds similar to 'wee wee.' To take a wicked yes is to take a wicked piss.
Teacher: "In French, when youy want to say yes, you say,'Oui oui.' "
Peter: "You gotta be freakin' kidding me! What do they say for no,'doo doo?' Hey, I'll be right back, I gotta take a wicked yes."