Breaking Bad waited five years to make one callback reference, and it was genius.
In Avengers: Endgame, when Captain America was about to fight Thanos’s army by himself, but then Sam appeared behind him ~on his left~, calling back to The Winter Soldier.
In Parks and Rec, when Leslie got a free MRI during her blind date with Chris in Season 2, and he said her body was capable of having triplets the first time she got pregnant. Then, in Season 6, she was pregnant with triplets.
In Breaking Bad, when Walter White rolled that barrel through the desert at the end of Season 5, he unknowingly walked right by the pants that he lost in the pilot.
In Split, when the final scene started playing, and Bruce Willis’s character appeared, revealing that the whole movie was actually a sequel to Unbreakable, which came out 16 years earlier.
In Sister, Sister, when the series had a full-circle moment by starting and ending with the same department store clerk thinking that Tia and Tamera were one person.
In Community, when they spent the first two seasons casually mentioning the name “Beetlejuice,” and after the third time, an actual Beetlejuice appeared in the background, just like he did in the movie.
In Seinfeld, when the pilot opened with a conversation about shirt buttons, and nine years later the finale ended with the same exact conversation about shirt buttons.
In Veep, when Selina and her team hoped that a big news event would happen — like Tom Hanks dying — to distract the media from reporting on her scandal in the pilot episode. Then, in the finale, Tom Hanks’s death overshadowed the news of her own funeral.
In Final Destination 5, when the movie ended with Sam boarding his flight to Paris, and you realized it was the same plane that exploded after takeoff in the first Final Destination.
In Grey’s Anatomy, when Dr. Miranda Bailey had to give birth without her husband in Season 2, so George stepped in to help her. Then, 14 years later, Bailey returned the favor and repeated the same mantra to Amelia so she wouldn’t feel alone while giving birth.
In American Horror Story: Apocalypse, when Madison Montgomery returned five years later and repeated her iconic “Surprise, bitch” line from AHS: Coven.
In How to Get Away With Murder, when the pilot’s first scene and the finale’s ending scene were practically identical, except Annalise Keating was replaced by Christopher.
In Deathly Hallows Part 2, when Harry, Ron, and Hermione fought the same creatures during the Battle of Hogwarts that they fought throughout the series, in the exact order that they appeared throughout each movie.
In Lost, when the final scene of the show perfectly mirrored the pilot’s intro from six years earlier, except everything happened in reverse.
In the Toy Story series, when the aliens spent the first movie worshipping “the claw,” and then, in the third movie, they used it to save everyone from being burned alive in the fire.
In Modern Family, when the final scene of the series perfectly mimicked the first scene of the series by putting each character in the same situation they were in 11 years earlier.
And in 30 Rock, when they had a running gag that Kenneth might be immortal, so in the finale’s post-credits scene, they showed him 100-plus years in the future with flying cars.
Note: Some responses have been edited for length and/or clarity.