15. Nobody Reads These Anymore (Season 13, Episode 2 - The Parent Rap)
One of the show's many meta-gags referencing the series itself, this is a clear jab at the fact that The Simpsons' lengthy opening sequence feels pretty perfunctory by its thirteenth season, and surely a lot of viewers simply skip past it to save themselves a minute of their lives. For the few who actually bothered to sit there and watch it, it's a nice little Easter egg "reward".