Many of the Zombie extras are fans of the TV series Spaced, which also starred Simon Pegg and Nick Frost and was also directed by Edgar Wright. They were recruited through the Spaced Out fan web site to be in the film.
The phrase "fried gold" originated behind the scenes of Simon Pegg, Jessica Hynes and Edgar Wright's sitcom Spaced and was mentioned several times on the DVD commentaries for that series. It makes several fan-pleasing appearances in the film.
The zombie that Shaun (Simon Pegg) and Ed (Nick Frost) find in their garden is Mary, the checkout girl from the film's credit montage. A short story detailing her transformation into one of the undead was featured in issue 1384 of the classic British sci-fi comic 2000AD. The issue went on sale 7 April 2004. The strip was called "There's Something About Mary" and was written by Simon Pegg and Edgar Wright (the film's co-writers) with art by Frazer Irving.
In the beginning of the film, when Shaun is riding the bus, the young man in front of him is listening to music. The song that can be heard is the dance club classic "Kernkraft 400" by Zombie Nation, whose melody is borrowed from the song "Stardust" (the theme for the C64 game, Lazy Jones).
When Shaun and the group are running out of Liz's flat they are all carrying weapons of some kind, but only Shaun actually hits any zombies. This was because only the cricket bat that Shaun was carrying was a padded fake, all the other items were real and would have hurt the extras playing zombies if they had been hit with them.
John and Bernie run the Winchester. These are the real names of the landlord and landlady who used to run Simon Pegg's local pub, the Shepherds in Highgate. John used to make toasted sandwiches for regulars, hence the reference to "the Breville out back." Pegg and Nick Frost were regular attendees of the Shepherd's Thursday night quiz, hence the line "we do the quiz" when Shaun is knocking on the Winchester's door. Chris Martin of Coldplay, who plays a zombie in the film, also used to attend quiz night.
When Shaun's girlfriend objects to going out to the Winchester he suggest a few other pubs, one of which is the Shepherds, which actually used to be Simon Pegg's local pub in Highgate until it was closed and reopened as a themed bar.
Shaun berates Ed for calling the creatures zombies ("the zed word," which they are, of course). This alludes to the curious fact that many of the most iconic zombie movies (including Night of the Living Dead and Resident Evil) never feature the word "zombie" at all. It can also be a reference to Danny Boyle, director of 28 Days Later..., and his insistence that it isn't a zombie movie.
On the DVD (at least the region-two and region-one versions), there is a feature that plays an edited version of the scene where Pete yells at Shaun and Ed for playing the music too loud ("I've got to go to fucking work in four fucking hours!") that has been dubbed over for television airings, thus replacing all obscenities. "Fuck" is replaced with "funk," "prick" becomes "prink." The feature has the fitting title "Funky Pete" and is found in the alternate bits section.
A poster in Shaun's flat is an image from the Edgar Wright-directed video for Psychosis Safari by 'The Eighties Matchbox B-Line Disaster'. Members of the band feature as zombie extras and a song of theirs, "Mr. Mental", is featured on the soundtrack album.
When Noel (Rafe Spall) rings Ed (Nick Frost), Ed calls him Noodle, which is the name of one of the teenagers in an episode of Spaced. Noel also says, "E-Ball says you're holding," which is a reference to director Edgar Wright, whose nickname is E-Ball.
The Battle Royale poster in Shaun's living room is designed by Fred Deakin of Airside, as is the green poster with the flowers and girl in Liz's flat. Deakin is also a member of the band 'Lemon Jellÿ', which provides music for the soundtrack.
Just when Shaun is exiting the Indian-run deli, which is tuned to a radio station playing songs from Indian movies, the song stops and a newscaster begins speaking in Hindi. The content of the news, when translated in English, is, "People are waking up from their graves."
When Shaun and his friends are trying to get inside the pub, horror writer and Frightfest organizer Alan Jones can be seen as a zombie walking past the phone box. He's the bald one in a checkered shirt.
Among the voices in the news reports you hear on television and radio you hear David Walliams on a TV news broadcast, Mark Gatiss on the radio, Keith Chegwin hosting the "Fun Dead" programme, and Rob Brydon voicing the "Zombies From Hell" show at the end. Also, the voice heard at the end dismissing the infected monkeys being the cause is Edgar Wright.
Northern Irish rock band Ash donated 3 songs used in the film: "Meltdown", "Orpheus" and "Everybody's Happy Nowadays" featuring Chris Martin. These songs were donated for free as Edgar Wright's girlfriend, Charlotte Hatherley, played guitar and sang backing vocals for Ash at the time.
When Shaun is heading to the shop for the first time, a worker on the street is listening to the radio. The newscast mentions a space probe that unexpectedly re-entered the Earth's atmosphere and broke up over England. This is likely a reference to Night of the Living Dead in which radiation from a satellite returning from Venus was given a possible cause for the dead returning to life.
during the Remembering Z-Day montage, there is a long shot of the zombies walking through a park; Edgar is the one in black who falls over himself. He also makes a voice cameo as the host of Fulci's Italian restaurant.
The trivia items below may give away important plot points.
Chris Martin of Coldplay, who appears as himself on a news report near the end of the film promoting ZombAid, also plays a zombie. After Shaun and Liz escape from the basement of the Winchester, he can be seen playing the zombie walking past the phone booth from right to left.
According to writer-director Edgar Wright in the DVD commentary, when Ed attempts to cheer Shaun up at the Winchester with plans of binge drinking, he is actually summarizing the events of the next day (Z-day) entirely in drinking references. "Bloody Mary" - Checkout Girl, "Bite at the king's head" - Phillip, "Couple" - David and Di, "Little Princess" - Liz, "Stagger back" - impersonate zombies, "Bar For Shots" - firing rifle.
Even though according to the zomb-o-meter feature stating that Di dies, the DVD's animated special feature Plot Holes: What Happened to Dianne When She Left the Winchester? explains that Di makes it through the crowd of zombies, climbs a tree, passes out, awakens to utter silence and out of fear stays in the tree surviving on Dave's severed leg, and eventually going to live with an aunt.
When Shaun and Ed are listening to Electro, Pete tells Ed if he "wants to live like an animal, he can live in a shed". Later, Shaun keeps Ed in the shed at the end of the film after he becomes a zombie.