In season 11, ep. 10, when Peggy gets amnesia, Al eventually becomes interested in her again by the end of the episode, and quickly went back to being disgusted by her when she regained her memory. This implies that Al doesn’t find Peggy so repulsive because of her looks (frankly, Katey Segal is a very good-looking woman), but because of her repulsive personality.
It was heavily implied that Al was a major jerk and asshole in high school. The 'Bundy Curse' and his status as an eternal loser, are Karmic justice for that behavior. Al ensures his status in life never changes by continuing to act like a jerk. The more he lashes out about his crappy lot in life, the worse his life is.
Seven appearing on the milk carton was obviously a lampshade, but in-universe, this means Seven just went missing one day and nobody cares about finding him! (And no, this isn't Fridge Horror, since that term implies that somebody out there would be horrified by the idea of Seven going missing.)
Al Bundy peaked in high school, Polk High. James K. Polk is remembered for fulfilling all of his campaign promises in his first term, not seeking a second term, and promptly dying shortly after leaving office. Like Al Bundy, Polk peaked early and then crashed.
Kelly has many groups of friends, who change in almost every episode that they appear. You may wonder why, but then "The House That Peg Lost" implies a reason; she sleeps with all their boyfriends.
In their first Christmas episode from season 2, "You Better Watch Out", after the Santa Claus who accidentally fell to his death is taken away, his bundle of mall certificates fall off the roof and the Bundys soon take the whole bundle with them to spend for themselves for Christmas. Not only do the merchants at the mall have the right to refuse the family to use all of the certificates, but even worse, upon realizing that the guy they hired as Santa is dead, they could be accused of killing him just to steal his money!