Many of the zombie extras are fans of Spaced (1999), which also starred Simon Pegg and Nick Frost, and was also directed by Edgar Wright. They were recruited through the Spaced Out fan website to be in the film.
Just when Shaun is exiting the corner shop, 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."
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 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 (1968), in which radiation from a satellite returning from Venus was given a possible cause for the dead returning to life.
The zombie that Shaun and Ed 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 number 1384 of the classic British science fiction comic 2000 A.D. The issue went on sale April 7, 2004. The strip was called "There's Something About Mary" and was written by Simon Pegg and Edgar Wright, with art by Frazer Irving.
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.
Near the beginning of the film, when Ed is playing on the Playstation 2, Shaun directs him (top left, reload, good shot, et cetera). When the gang are in the Winchester pub and Shaun is firing at the zombies, Ed repeats exactly what Shaun instructed him to do during Timesplitters 2 (2002).
DIRECTOR CAMEO (Edgar Wright): 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.
Simon Pegg and Edgar Wright considered a sequel that would replace zombies with another monster, but decided against it, as they were pleased with the first film as a stand-alone product, and thought too many characters died to continue the story. The proposed title was From Dusk till Shaun.
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.
Shaun berates Ed for calling the creatures zombies. This alludes to the curious fact that many of the most iconic zombie movies (including Night of the Living Dead (1968) and Resident Evil (2002)) never use the word "zombie" at all. It can also be a reference to Danny Boyle, Director of 28 Days Later... (2002), and his insistence that it isn't a zombie movie.
Among the voices in the news reports you hear on television and radio you hear David Walliams on a television news broadcast, Mark Gatiss on the radio, Keith Chegwin hosting the "Fun Dead" program, 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.
The morning of Z Day, as Shaun is flipping through the channels, the few words that we hear from each channel, together form a full sentence explaining what's been happening. "Although no one official is prepared to comment, religious groups are calling it Judgement Day. There's..." "...panic on the streets of London..." "...as an increasing number of reports of..." "...serious attacks on..." "...people who are literally being..." "...eaten alive..." "...but witness reports are sketchy. One unifying detail seems to be that the attack has, in many instances, appeared to be..."
When Edgar Wright and Simon Pegg began pitching the film, Film4 Productions showed interest in it. Then, Film4 significantly cut back its budget, leaving the film without a production company for a while. Because Wright was still hoping to get the film made, he held off on taking other directing jobs while searching for new financing for the film, and ended up having to borrow money from his friends. "For me to take on a television job, meant that I was like pushing the film back, so ... I was going rapidly broke. I was like majorly in the red." According to Wright, Pegg still hasn't allowed him to pay back the money he owes him from those lean times.
When Shaun is at work, he is showing a couple the televisions. As he is flipping through channels, we see Trisha Goddard with a woman guest, and a game show. At the end of the movie, this same woman and game show will be seen on television. The woman who is dating a zombie, and zombies attached to bungee cords.
The phrase "fried gold" originated behind the scenes of Simon Pegg, Jessica Hynes, and Edgar Wright's sitcom Spaced (1999), and was mentioned several times on the DVD commentaries for that series. It makes several fan-pleasing appearances in the film.
Northern Irish rock band Ash donated three 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.
As this is the first part of the unofficial Three Flavors Cornetto Trilogy, the red wrapper (strawberry flavor) makes its appearance in the film. According to Edgar Wright, red represents the blood and zombies, which is the main motif in the film. For Wright's other films, Hot Fuzz (2007), it was blue and vanilla flavor, representing the Police while the final part, The World's End (2013), it was green and peppermint with chip representing science fiction and extraterrestrial elements.
According to Edgar Wright, the reason that Cornettos appear in the film, is because he once ate a Cornetto to get over a hangover, and thought it would be funny if Ed, did the same after a night of drinking.
When Noel rings Ed, Ed calls him Noodle, the name of one of the teenagers in an episode of Spaced (1999). Noel also says, "E-Ball says you're holding," which is a reference to Edgar Wright, whose nickname is E-Ball.
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.
In the film, Shaun's mother calls him "pickle", and apparently that's not just something the filmmakers made up. Edgar Wright's own mother called him that as a boy, apparently while she taught some of his classes at school, much to his embarrassment.
At the end of the movie, there is fake movie trailer about a boy named Ramirez who, using a shotgun, fought off his entire zombie family. This is a spoof of the Menendez brothers who murdered their parents with a shotgun in August 1989.
Near the beginning, when Shaun is leaving the shop where he gets a can of Coke and the Cornetto, there is a pizza place behind him and to his left. The name of the restaurant is "Bub's Pizzas", probably a reference to the main, chained-up zombie (who's taught to hold and point a gun) in Day of the Dead (1985). In that film, the doctor named that zombie "Bub".
The film was inspired by Spaced: Art (1999), in which Tim, under the influence of amphetamine and Resident Evil 2 (1998), hallucinates that he is fighting off a zombie invasion. After the episode was filmed, Edgar Wright pitched the idea of a feature-length zombie comedy.
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 "It Happened Then/Babylon Run" (by Dave Eager and Pete Baker), which is the theme for the "Star Dust" sub-game of the C64 game, Lazy Jones.
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 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.
When the team is barricaded at the pub, Ed (Nick Frost) turns on a loud slot machine, which Shaun (Simon Pegg) promptly turns off by pulling the plug. Before he does so, the few musical notes indicates that the song theme is "Phantom of the Opera", a weird choice since the game is clearly named "Dracula". The fruit machine is made by Barcrest, and is called "OOH AH DRACULA", and features in this movie, Hot Fuzz (2007), and The World's End (2013).
When Joe Cornish is on-screen, we see Lucy Akhurst (Sophie in season two of Spaced (1999)) as a zombie getting shot in the back. She's the blonde girl in the center of the screen, with Cornish to her right.
In the beginning, after Liz splits up with Shaun, the jukebox in the Winchester plays "If You Leave Me Now" by Chicago. Ed says, "Who the hell put this on?", and Shaun replies, "It's on random." Later in the Winchester it plays "Don't Stop Me Now" by Queen, Shaun says, "Who the hell put this on?", and Ed replies, "It's on random."
The Battle Royale (2000) 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 Jelly, which provides music for the soundtrack.
The trivia items below may give away important plot points.
According to 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? (2004) 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. Ed also says, "Next time I see him, he's dead." Next time Ed sees Pete, he's a zombie.
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.
When the group are in the Winchester and Shaun has returned from distracting the zombies, David questions his motives as to why they are in a pub, he refers to Ed as Shaun's "boyfriend". Ed hands Shaun a beer who replies with "Thanks, Babe". This is a common conversation between the two in Spaced (1999), which was also directed by Edgar Wright.
During cast commentary at the end of the movie just before the credits, Simon Pegg makes a possibly joke reference to a sequel that is coming soon titled "Shaun of the Dead 2: From Dusk Till Shaun". This never happened, but it may have been the plan before the "Blood and Ice Cream Trilogy" ideas were founded.
When the zombies are making their way into the Winchester, Shaun shouts to Ed, "Get behind me, get behind me!" the same way Han Solo shouts to Chewbacca as Stormtroooers are entering the Death Star in Star Wars: Episode IV - A New Hope (1977), one of Simon Pegg's favorite films.
After Shaun (Simon Pegg) joins Ed (Nick Frost) at the Winchester, after his girlfriend broke up with him, Ed uses his "Clyde impression" (Clyde, the orangutan from Every Which Way But Loose (1978) and Any Which Way You Can (1980)) in an attempt to make Shaun feel better. Later in the movie, when Ed is being bitten by two zombies, his cries of pain ring similar to orangutan sounds.
The pub shooting at the end where Shaun shoots and Ed directs him on where to shoot is a reversal on the scene in their house with Ed playing a Shooter game, and Shaun directs him on where to shoot (e.g. "Top Left")