1.On Parks And Recreation, the drunk man Leslie shoos out of the playground is the same man who returns in the final episode to ask for a playground swing to be fixed.
2.On Spongebob Squarepants driver's license, his height and weight is comparable to that of a real-life sponge.
3.On Daredevil, Matt Murdock visits a police station, and behind him is a sign that reads, "You don't have to reveal your identity to help stop violent crime."
4.On Game Of Thrones, Daenarys's hair features more braids as she wins more victories, as Dothraki tradition dictates.
5.On Community, the word "Beetlejuice" is spoken three separate times over three seasons. After the third time, he walks by in the background.
6.On Breaking Bad, Walt Jr. complains to his mom that she bought the wrong kind of cereal — a mistake she fixes later on.
7.On an episode of Gravity Falls, Tyler has trouble deciding which of two shirts to wear. Later on, we see he bought both shirts and simply sewed them together.
8.On an episode of Supernatural, Misha Collins (playing himself) sends a tweet to his followers. The day the episode aired, the actor posted the exact tweet to his followers.
9.During Season 2 of The Simpsons, Mr. Burns gifts the family a gigantic head statue. In Season 28, the statue is shown being stored in the basement.
10.On episode of Bones, an X-ray of Homer Simpson's head appears in the background.
11.On 30 Rock, Liz admits she doesn't own any green clothing; a season later, she explains why.
12.On an episode of Broad City, Abbi spends more than she can afford on a dress, so she gets her money's worth by wearing it to every nice occasion from that point forward.
13.On Arrested Development, characters often sit on bench advertisements in ways that hint at future plot points.
14.On Bojack Horseman, Beyonce falls down in one episode; the next time we see her, she's wearing a cast.
15.On the Season 5 premiere of Brooklyn Nine-Nine, Hitchcock takes off his shirt, revealing a tattoo of himself with a gun in his mouth...
...It's a callback to the previous season, when he gets the episode to show how cool he is — he thinks it's a tattoo of him blowing smoke off the gun barrel.
16.On The Office, there's a disturbing clown painting that's bolted to a wall so it seems impossible to remove. But it appears they were eventually able to get it down, as the same painting appears in a later episode at a garage sale.
17.And on Frasier, the man who delivers Martin's chair in the first episode is the same guy to pick up the chair in the finale episode.