S6E19 : Substitute

When the gang sees Mitch at a putt putt course, they laugh it up at his pathetic job until they accidentally hit him in the head with a golf ball. Feeling sorry for him, Eric invites him to join the gang in the basement. But it snowballs from there when Mitch obsesses over Donna. Meanwhile, Pam doesn't see what the big deal is about rejecting Bob's offer to move in together, since she is dating another man.