1. Most people would have missed this subtle piece of humour by the set designers.
2. If the walker that briefly appeared right after Mearle's death looked familiar, that's because it was designed to look like the poster zombie from Dawn of the Dead.
3. The show is littered with references to Dawn of the Dead and even contained a shot-for-shot remake of this iconic zombie death.
4. And Dawn of the Dead isn't the only George A. Romero movie paid homage to on the show.
During the gang's escape from Terminus, a crate can be briefly seen inscribed with the same words as the one that plays a pivotal role in the legendary director's 1982 horror movie Creepshow.
5. While only an error, this thirsty zombie taking a drink is still worth a look.
6. Anyone who thought to read the Bible passages displayed in Father Gabriel's church would have been well-rewarded.
7. And that's not the only reference to the undead hidden inside.
8. Even those familiar with the comics probably missed this cameo from everyone's favourite baseball bat, Lucille.
In the comics, Lucille is the name given to a barbwire-wrapped baseball bat wielded by antagonist Negan. Could this be a hint toward the impending arrival of many fans' favourite villain?
9. In this scene, some blue meth (famous from AMC’s other hit show, Breaking Bad), makes an appearance.
10. And meth isn't the only thing to cross over from Breaking Bad.
A Dodge Challenger SRT8, the same car Walter White bought Walt Jr. on Breaking Bad, shows up. Given that the last we saw of the car on Breaking Bad was it being blown up by Walt, it seems unlikely it's the same car, although hopes for a Breaking Bad/The Walking Dead crossover with Jesse Pinkman traveling across a post-apocalyptic wasteland calling zombies "bitch" remain undamaged.
11. The famous fictional cigarette brand Morley exists in The Walking Dead universe.
The fictional brand had appeared on many TV shows over the years, but most famously as the brand of choice of The X-Files character The Cigarette Smoking Man. Perhaps another nod to Vince Gilligan?
12. There's a street called Morgan in Alexandria.
13. Recognise one of the decapitated heads in The Governor's macabre collection?
That could be because it contains the severed head of the Jaws character/corpse Ben Gardner.
14. Rick’s new police uniform in Alexandria contained a familiar phrase.
15. The Walking Dead comic creator Robert Kirkman's other hit comic, Invincible, has appeared on the show.
16. Sometimes a regular, run-of-the-mill zombie just isn't good enough to get that fatal kill bite.
17. Clocks often point to the number of the episode and season they appear in.
18. During Tyreese's dying hallucinations, an English accent could be heard giving a radio announcement. That voice belonged to none other than Andrew Lincoln.
19. Remember Sam, the guy locked upstairs in a house with his girlfriend during Season 4? He made a return, albeit only briefly.
20. Even celebrities aren't safe in the event of a zombie apocalypse.
Anthrax guitarist and Walking Dead fan Scott Ian made a brief cameo as a member of the undead during the show's fifth season.