When Will and Keith are sitting in the living room playing games there is a product placement of two cans of Mello Yello prominently displayed on the table. At the time of the show, the citrus drink was widely available only in the American Midwest and Southeast while The Coca-Cola company didn't expand nationwide until 2010. While Philadelphia is not part of the Midwest, it's close enough that Keith likely brought the cans with him for Will.
Will makes a knock-knock joke about Amy Fisher. This is in reference to the much publicized incident where Fisher went to the home of her lover Joey Buttafuoco, then shot his wife Mary Jo Buttafuoco in the face when Mary Jo answered the door.