- Awesome, Dear Boy: Reportedly, Colin Firth had always wanted to play a Bond-like spy.
- Billing Displacement: Taron Egerton plays Eggsy - the main character, but you wouldn't know it by looking at the film's poster - his name isn't even mentioned while Colin Firth, Michael Caine & Samuel L. Jackson all get Billed Above the Title. Even more so in the film's credits — he's not even one of the first five names (Due to characters being listed in order of appearance).
- Dueling Movies: With Spy, The Man from U.N.C.L.E. (2015) and Spectre.
- Dyeing for Your Art: Egerton and Firth went through six-months long training regimes to be able to perform their own stunts.
- Enforced Method Acting: As Matthew Vaughn revealed in the "Anatomy of a Scene" video during the underwater test, everybody's looks of panic is completely real. Absolutely no CG or breathing apparatuses were used- they all were sitting ducks underwater waiting for Taron Egerton to break the glass to let them out (Taron's enraged punching, as you may have guessed, was also completely real).
Adding to the fear was the fact that the mechanism that lowered the set into a giant pool malfunctioned. It was meant to stop at set intervals so that multiple takes could be shot before being lowered to another depth (and repeated) until all the necessary dialogue was shot, but something went wrong with the computer programming and the set descended all the way very quickly on the first take, nearly drowning the cast and ruining the equipment.
- Fake Brit: Mark Hamill plays the British Professor James Arnold with a spot-on accent.
- Fake Nationality: Bjørn Floberg, who plays the Prime Minister of Sweden, is Norwegian.
- Fake Scot: Mark Strong as Merlin.
- In Memoriam: The film's closing credits dedication states: "In loving memory of my mother Kathy [Kathy Ceaton], who always put the extra into ordinary and taught me what a Kingsman should be". Ceaton is the late mum of the film's director Matthew Vaughn.
- Meaningful Release Date: The film opened on Friday the 13th, the day before St. Valentine's Day. Valentine himself even calls his the start of his "new era", Valentine's Day!
- No Stunt Double: Colin Firth did eighty percent of his own stunts, according to Stunt Coordinator and Second Unit Director Bradley James Allan.
- Playing Against Type: And a lot of it:
- Samuel L. Jackson, who usually plays Scary Black badasses, plays a slightly Adorkable albeit megalomaniacal technology mogul with a lisp who has no stomach for blood or violence.
- Colin Firth is best known for his dramatic work in British cinema, whereas here he plays an Action Hero who can take down an entire church congregation without breaking much of a sweat. Many critics and viewers were pleasantly surprised by Firth's ability to play a badass.
- Mark Strong, who almost invariably plays intimidating villainous roles, is cast here as the Kingsman organization's deadpan techie and he remains a good guy to the end.
- Michael Caine primarily plays benevolent, kind-hearted gentlemen. Arthur is a gentleman at first glance only, since he's actually an elitist prick who is working with Valentine and even lets the f-bomb slip while dying of poison. However, this was by no means Caine's first time playing a villain. Films where he plays a villainous role include Dressed to Kill, Mona Lisa, On Deadly Ground (where he also plays an elitist prick, probably far worse and less subtle than Arthur) and the remake of Get Carter.
- Release Date Change: The picture was originally going to be released late 2014, around late October or November, depending on the territory, but the movie was not ready, so the worldwide release launches got pushed back to dates, most of which, are during February 2015.
- Star-Making Role:
- For Sofia Boutella, leading her to be cast in high profile roles in Star Trek Beyond and The Mummy (2017).
- For Taron Egerton who went on to star in Eddie the Eagle, was cast as the lead in a new Robin Hood film, and was considered for the young Han Solo.
- Sophie Cookson, who played Roxy, also got a big lift from the film, although her career hasnt been as prolific as Egertons or Boutellas.
- Sleeper Hit: The movie wasn't expected to do as well in the United States as it did, with some citing the movie as being "too British" to catch on with American audiences, not to mention being a hard-R adaptation of a comic property, which tend to not do well. It was also put up against the juggernaut Fifty Shades of Grey franchise's first film. And yet, it made more than its entire production budget in the USA alone.
- Throw It In!:
- Samuel L. Jackson wound up lisping in his first take. Matthew Vaughn decided to incorporate it into the Valentine character (which not only makes it funnier, but fits how Bond villains have a talking or physical distinction).
- The Kingsman agents' distinctive eyeglasses were simply patterned after the pair Matthew Vaughn wears. Michael Caine didn't realise this at first, and thought it was a Shout-Out to his own role as Harry Palmer.
- The church brawl is set to Lynyrd Skynyrd's "Free Bird" because it was one of the first results that came up when Googling for long guitar solos.
- What Could Have Been:
- Aaron Taylor Johnson was offered the role of Eggsy before Taron Egerton was cast, but turned it down due to scheduling commitments to Godzilla (2014). Johnson would eventually go on to be cast in The King's Man.
- Emma Watson and Bella Heathcote were considered for the role of Roxy before the casting of Sophie Cookson.
- Leonardo DiCaprio, Idris Elba, and Tom Cruise were considered for the part of Richmond Valentine before Samuel L. Jackson was cast.
- Amy Purdy was originally cast as Gazelle before the casting of Sofia Boutella, but dropped out when filming was delayed, so she wouldn't miss the Olympics.
- There were going to be more celebrities who were held prisoner at Valentine's base, including Lady Gaga and Elton John. John later appeared in the sequel Kingsman: The Golden Circle.
- What became the Kingsmen for the movie was MI6 in the comic and when originally pitched to Marvel, the agency was S.H.I.E.L.D. Imagine if the film had been directed by Joss Whedon and tied into the TV series and the rest of the Marvel Cinematic Universe.
- There was originally a flashback scene set in 1975 which used CGI to show Michael Caine 40 years younger (much like Jeff Bridges in the opening scene of TRON: Legacy), Matthew Vaughn said it was removed because it "turned the film's pacing sideways".
- The church massacre scene originally ran for seven minutes with no cutaways in an early cut of the film rather than the three and half minute version with cutaways to other characters seen in the final cut. It was cut down as the scene was just too over the top and gory for even the makers of the film. Many fans are hoping the uncut version will appear on the DVD / Blu-ray release even though there are no current plans to release it.
Also, its original soundtrack was Guns N' Roses' "November Rain", given said video features Slash playing his solo in front of a church. But then Matthew Vaughn realized the solo was too short, Googled "long rock solos" and went on to Lynyrd Skynyrd's "Free Bird".
- Merlin was originally going to speak in a Welsh accent, but Mark Strong found it a bit too challenging and persuaded Vaughn to let him use a Scottish accent instead.
- The Kingsmen were going to kill the dogs, before Jane Goldman rewrote it to have them shoot blanks at them, in order to avoid losing audiences.
- Word of God:
- Vaughn has confirmed that the President seen in the film is not a depiction of Barack Obama.
- E (the man Valentine calls during the third act about satellites) is in fact South African-American inventor Elon Musk.
Trivia / Kingsman: The Secret Service