1.The title screen during the opening credits decays a little every season.
2.There's a creepy face in a tree during the first episode.
3.Edwin Jenner's warning to Rick in the Season 1 finale is the title of the Season 7 premiere episode, in which Rick and his group meet Negan and reach their low point.
4.What Merle says while stuck on the roof is the same as what he says right before the Governor kills him.
5.There's a Spam knockoff called "SMEAT."
6.The Governor stumbles across a beheaded corpse with a sign nailed to it that reads "LIAR." In the next episode he says nothing but the word "liar" immediately before beheading Hershel.
7.The van Daryl and Carol enter that's teetering on a bridge and has a Virgin Mary statue inside is a reference to the Lost scene in which Boone enters a plane teetering high above, filled with Virgin Mary statues.
8.In Season 4, Beth and Daryl stumble upon a bunch of bodies being eaten by walkers. Near one of them is a baseball bat wrapped in barbed wire, just like Negan's beloved Lucille.
9.The guy Rick walks in on in Season 4's "Claimed" wasn't using the toilet, he was doing coke.
10.The clock in Season 4's "Indifference" reads 4:20.
11.This shot of the Governor lying on a parrot pillow makes him look like a pirate.
12.When Tyreese is hallucinating in Season 5's "What Happened and What's Going On," he hears a British voice on the radio. It's actually Andrew Lincoln speaking.
13.The man in the red poncho who gets killed by the Wolves is a nod to the fairy tale of Little Red Riding Hood and the Big Bad Wolf.
14.Since losing his right eye, Carl has switched to shooting with his left hand.
15.This art hanging behind Morgan in Season 6's "Last Day on Earth" foreshadows the Kingdom.
16.The Bible verses in Father Gabriel's church revolve around the dead.
17.In Season 5's "Conquer," Aaron kills a walker with a machete, re-creating a shot from Dawn of the Dead.
18.Shortly after Enid eats a turtle, Eastman wears a shirt that says "Save Terrapins."
19.Daryl gives Carol a Cherokee rose to make her feel better when Sophia's missing; four seasons later, one can be seen on a walker killed by Daryl.
20.What Morgan says to Rick in the first episode, Rick says back to Morgan when they're reunited in Season 6.
21.In Season 7's "New Best Friends," something quickly zips by behind Rick — and it could've been a plane (cool), a UFO (cooler), or a production mistake (not exciting, but feasible).
22.In Season 7, Rick tells Michonne something very similar to what Glenn told her in the past.
23.Negan talking about sleeping with widows infuriated Rick on Maggie's behalf, but it also reminded him of Lori and Shane, whom he discusses with Michonne.