The scene where Homer is staring at a newspaper looking for codes is a reference to the film A Beautiful Mind.
John Lennon's "Mother" plays in the background, making him the fourth and final Beatle to have his voice in the show. The first was Ringo Starr in Brush with Greatness (1991), then George Harrison in Homer's Barbershop Quartet (1993) and Paul McCartney in Lisa the Vegetarian (1995). John Lennon could never officially guest star, as he died in 1980 - 9 years before the series began.