We’ve discussed modern television, in which in-jokes, foreshadowing, and easter eggs can make binge-watching a whole season at a time on Netflix enjoyable on a whole new level. However, there appears to be almost a competition from 21st-century TV series to see who can conduct the most insane, longest-lasting, or most subtle easter eggs, and then wait to see how long it takes the viewing public to catch them. Cracked shows us the ones that have been found. In one example, the show Community took three years to summon Beetlejuice.
In one episode of each of the first three seasons, the word "Beetlejuice" was used off-handedly in a joke. If you've seen the movie Beetlejuice, the titular mischievous ghost (played by Michael "holy shit this guy used to be the biggest star in Hollywood?" Keaton) would appear in the world of the living if anyone said his name three times. So, sure enough, on the third mention by a Community character, this guy appears in the background for exactly two seconds:
It's a random person dressed as either Beetlejuice or Gary Busey. That they patiently waited three years to reach that punchline is staggering A) because it looked like the show was going to get canceled several times before that, and B) when you consider that some shows can last eight seasons and the only punchline is "Look! Nerds!"
But that’s far from the only long-ranging joke in Community, and there are five other shows with hidden extras that will blow your mind at Cracked. -via mental_floss