Rejected by every studio they approached, Matthew Vaughn raised the budget over dinner one evening and made the film independently. Vaughn eventually sold the film to Universal for a higher price than he had originally asked for.
Before going to Lionsgate Studios, the film's producers tried several other studios that gave the same ultimatum: "We'll take it, if you drop Hit Girl or make her nineteen."
The name of the main character, Dave Lizewski, was chosen at a charity auction held by Kick-Ass co-creator/writer Mark Millar before the first issue of the comic was published. The winner of the auction chose the name to be used himself.
In the comic book, Big Daddy's backstory of being a former cop was a lie. He was an accountant bored with his life who kidnapped his daughter and turned her into an outlaw. Many fans preferred the film version, including Mark Millar, who said it "would have messed up the structure of the movie." Comic book artist John Romita, Jr. stated that the story of Big Daddy in the film "works better stopping short… You love him better in the film."
Hit Girl's first introduction hadn't worked very well, so Chloë Grace Moretz's own mother (who was present on set throughout the shoot) suggested they go back to the comic book and have her daughter use the word "cunt."
Responding to criticism of Hit Girl's character, Chloë Grace Moretz said in an interview: "If I said even one of the words I say in Kick-Ass, I'd be grounded for years! I'd be stuck in my room till I'm twenty! I would never say that in a million years. I'm an average, ordinary girl." Moretz said that during the shoot she couldn't say the film's title out loud in interviews, calling it "the film" in public and "Kick-Butt" at home.
Before filming began, Chloë Grace Moretz trained extensively at a circus school in Toronto so that she could perform most of her own stunts.
Mark Millar actually prefers the film version to his own comic book.
For Big Daddy, Nicolas Cage modeled his speech patterns on Adam West from the original Batman (1966). According to Matthew Vaughn, Cage began delivering his lines this way at the first costume rehearsal. Vaughn, who said he was bothered by the harsh voice Christian Bale used in The Dark Knight (2008), stated that he was pleased Cage kept this performance in the film.
The comic montage of Damon Macready's, aka Big Daddy's, past life was drawn by artist and co-creator John Romita, Jr.
In the film's final lines, Red Mist says: "As a great man once said: Wait'll they get a load of me." He is quoting Jack Nicholson, who played the Joker in Batman (1989).
Big Daddy's line "Now go to Robin's revenge!" is a reference to a Robin comic book in which Robin fights a blind martial arts master. Despite being blind, his skill was so great that Robin couldn't even touch him. Robin managed to set up a whistle that would play automatically. This overloaded the blind man's primary sense and allowed Robin to sneak up behind him.
After Kick-Ass first meets Hit Girl, we see Big Daddy standing in front of a billboard featuring Matthew Vaughn's wife, Claudia Schiffer.
In the original comic book, Mark Strong's character was named "John Genovese." Genovese is one of the most powerful "Five Families" of the mafia (Bonanno, Colombo, Gambino, Genovese and Lucchese), and to avoid any trouble with them the name was changed to Frank D'Amico, which also nods to The Simpsons (1989), since Springfield's mob boss Fat Tony was named Anthony D'Amico.
Nicolas Cage suggested that his character's "disguise" would have Damon Macready with a mustache, while "Big Daddy" would have an even bigger mustache by means of adhesive extensions.
Matthew Vaughn deliberately chose not to seek funding from any of the major studios because he wanted to make an unrestrained, ultra-violent comic book film. He thought this way he would be free of unwanted interference and "studio notes."
The credits give explanatory names to many of D'Amico's "goons" for accurate character attributions. Five of these thugs, listed as "Posh," "Scary," "Sporty," "Ginger" and "Baby," were named after each of the Spice Girls.
The Marv logo at the opening of the film was designed by Matthew Vaughn's children.
Matthew Vaughn made the film for free, but on the condition that he be given the Mist Mobile after filming was completed. In reality, he thinks the car is too powerful to be drivable.
In the original comic book, Kick-Ass doesn't end up getting the girl.
Before Nicolas Cage was cast, Daniel Craig and Mark Wahlberg were considered for the role of Big Daddy.
Brad Pitt, a close friend of Matthew Vaughn, was initially going to play the role of "Big Daddy" but instead decided to take a role in Quentin Tarantino's Inglourious Basterds (2009).
The rights to the film version were sold before the comic book was first published.
Christopher Mintz-Plasse (Red Mist) originally auditioned for the role of Kick-Ass.
Big Daddy's costume is inspired by the uniforms worn by French riot police.
The music in the rescue scene (with the flashing lights) is John Murphy's Adagio in D Minor, which was originally written for and featured in the Danny Boyle film Sunshine (2007), in which Mark Strong also appeared.
According to Mark Millar, the "C-word" moment in issue 3 of the comic ultimately convinced Matthew Vaughn that this was a worthwhile project.
In the online execution scene, the background behind Big Daddy and Kick-Ass is a copy of the wallpaper from the "execution of Frank" scene in the 1983 film "Scarface."
The track composed for Big Daddy's raid on Frank D'Amico's warehouse is based on "In the house, in a heartbeat." The song was first used in 28 Days Later (2002) and 28 Weeks Later (2007) and was composed by John Murphy. Minor changes were also made, and the Kick-Ass soundtrack version was titled "Big Daddy Kills."
It was the second most pirated film of 2010 (11.4 million downloads on BitTorrent), ahead of Inception (2010) (9.72 million downloads), which placed third. Avatar (2009) was number one (16.58 million downloads).
Christopher Mintz-Plasse had to learn how to use a gear shift for the "Mist Mobile" in the film. He said that after the film was finished, he completely forgot how to do it.
In a Reddit thread, Nicolas Cage explained that the voice he used for Big Daddy was based on Adam West.
In a deleted scene, Adam watches news footage.
Body Count: Seventy.
When the villains are about to burn Kick-Ass and Big Daddy alive on live television, one of them says, "Fire is good! Fire is our friend!" This is a quote from a scene in Mel Brooks's Young Frankenstein (1974), which is itself a parody of a scene in Bride of Frankenstein (1935).
The music playing when Kick-Ass first meets Hit Girl at Rasul's was a remake of "The Tra La La Song," the theme song of the late-60s children's show The Banana Splits.
It was noted that D'Amico wears orange. When Red Mist vows to carry on his father's legacy, he changes his costume to orange.
When the first clips went viral, family groups were in an uproar over 13-year-old Chloë Grace Moretz's aptitude for violence and the C-word.
Matthew Vaughn initially wanted Hit Girl's wig to be pink, but costume designer Sammy Sheldon thought purple would look better. In the end, she managed to win him over.
Mark Millar and Matthew Vaughn knew each other socially through Jane Goldman and her husband, but they began working together thanks to Thor (2011). Millar had sent Vaughn some suggestions for the Marvel adaptation, but Vaughn ultimately left that project. He came to Millar to see if he had any interesting ideas, which would lead to "American Jesus," which is almost a sequel to the Bible. While they were discussing it, Millar mentioned Kick-Ass, and he began sending Vaughn the first script of the comic.
The opening guitar notes of "The Corridor," played before Hit Girl kills the thugs in the hallway, are based on "Kryptonite" by the rock band Three Doors Down.
While Dave and his friends are watching a news report about "Red Mist," Chris D'Amico can be seen in the background.
Dexter Fletcher plays a gangster named Cody who drives a yellow Range Rover. In Matthew Vaughn's previous film Layer Cake (2004), he plays a gangster named Cody who drives a yellow Range Rover. It is unclear whether they are the same character.
In a 2020 podcast interview, Chloë Grace Moretz revealed that when she threw a high kick while wearing the Hit Girl costume, her pants tore. Fortunately, since she was wearing a skirt, there was no need to change. She also said that the domino mask fit tightly on her face and that she had trouble keeping her eyes open (she later wore a different black domino mask in the sequel).
Rapper Method Man, an avid fan of Mark Millar, expressed interest in appearing in the film.
The "bazooka" in the film is based on the US Marine Corps' 83 mm SMAW (Shoulder-launched Multipurpose Assault Weapon).
The scrolling board in the cinema advertises The Spirit 3, a reference to the nonexistent second sequel to The Spirit (2008).
Unlike Christopher Mintz-Plasse and Lyndsy Fonseca, who play high school students, Aaron Taylor-Johnson was actually still a teenager during filming. He was 19.
Production designer Martin Childs was fired by Matthew Vaughn early in the production because they were "not on the same wavelength." Russell De Rozario was brought in to replace him five days before filming began.
"Red Mist" is a term used to refer to a bomb disposal officer who is blown up by the bomb he is trying to defuse. Toward the end of the film, this is essentially what happens to the father of the "Red Mist" character, Frank D'Amico.
Mark Millar stated that Kick-Ass would not exist if it weren't for Glen Michael and the Cartoon Cavalcade series.
Nicolas Cage's character, Damon Macready, asks his daughter the name of John Woo's first feature film. Cage had previously worked with John Woo on Face/Off (1997) and Windtalkers (2002).
Mark Millar shared the idea for Kick-Ass with Matthew Vaughn when they met at the London premiere of Vaughn's film Stardust (2007).
The film's original Dutch certificate was twelve years. After several complaints and due to the language and violence in the film, the Netherlands Institute for the Classification of Audiovisual Media (NICAM) re-rated the film for ages sixteen and over in May 2010.
Matthew Vaughn's involvement with Kick-Ass (2010) largely came about as a reaction to his failure to secure the directing job on Hancock (2008).
A pair of silkscreens seen in D'Amico's apartment depicting a gun is a 1981-82 work by Andy Warhol titled "Gun," and it depicts how the gun became such an important part of American society following an attempt on Valerie Solanas's life in 1968. The piece was produced using only the gun shown on the right side (similar to the one Solanas used in the near-fatal attack). Evan Peters, who plays Todd in this film, later played Andy Warhol in American Horror Story: Cult.
The mob boss who takes the fall for Red Mist's plan is named Tony Romita. The artist of the source material is John Romita, Jr.
Hit Girl is estimated by a friend of Dave's to be eleven years old. The actress Moretz was thirteen during filming.
The night-vision Hit Girl scene is staged to look exactly like an FPS (first-person shooter) game.
In this film, Nicolas Cage's character is given the first name "Damon." In the original comic, the character is referred to only as Macready.
Chris was supposed to be seventeen years old. The actor Mintz-Plasse was twenty-one during filming.
Pop singer Mika wrote a song for the film: "We Are Young."
Aaron Taylor-Johnson, Evan Peters, Nicolas Cage and Lyndsy Fonseca all played roles based on Marvel characters. Taylor-Johnson played Pietro Maximoff/Quicksilver in a brief role in Captain America: The Winter Soldier (2014) and then in Avengers: Age of Ultron (2015), though the character took on a larger role. Peters coincidentally played the same character in the X-Men universe (and later in the MCU) in X-Men: Days of Future Past (2014), X-Men: Apocalypse (2016) and the miniseries WandaVision (2021). Cage played Johnny Blaze/Ghost Rider in Ghost Rider (2007) and then in Ghost Rider: Spirit of Vengeance (2011). Lyndsy Fonseca went on to play Angie Martinelli in Agent Carter (2015).
Mark Strong later collaborated with director Matthew Vaughn on Kingsman: The Secret Service (2014) and Kingsman: The Golden Circle (2017).
Katie mentions the Scott Pilgrim book series. Nicolas Cage's cousin Jason Schwartzman appeared in the film adaptation Scott Pilgrim Vs The World.
Kevin Bacon is a big fan of this film. After watching it, he immediately accepted the role of Sebastian Shaw in Matthew Vaughn's X-Men: First Class (2011).
Evan Peters would later play Peter Maximoff/Quicksilver in 20th Century Fox's X-Men films, starting with X-Men: Days of Future Past (2014). That film was written by Matthew Vaughn and Jane Goldman, who are also the writers of this film. Vaughn also directed an X-Men film, X-Men: First Class (2011).
Joe Gilgun was offered a role in this but had to turn it down because of the programme Emmerdale.
Note that Mark Strong's gangster character always wears orange.
A cameo scene starring Glen Michael was arranged.
Evan Peters appears in this film alongside Nicolas Cage, who once owned The LaLaurie Mansion, "The most haunted house in America," built by Marie Delphine Macarty A. K. A. Madam LaLaurie. The LaLaurie Mansion and Madame LaLaurie inspired American Horror Story: Coven, in which Evan Peters appeared.
In one scene, while talking with Dave about comics, Katie says she has read the Scott Pilgrim comics. Coincidentally, the film adaptation of Bryan Lee O'Malley's comics, Scott Pilgrim vs. The World (2010), came out the same year this film was released. This film also features many actors known for playing superheroes, such as Chris Evans (Captain America - Marvel), Brandon Routh (Superman - DC), Mary Elizabeth Winstead (Huntress - DC) and Brie Larson (Carol Danvers - Marvel). Among them, Chris Evans appeared alongside Aaron Taylor-Johnson in Avengers: Age of Ultron (2015).
When Todd (Evan Peters) and Marty (Clarke Duke) first watch the Kick-Ass YouTube clip in the comic book cafe, a poster for the Avengers comic series can be seen in the background. Aaron Taylor-Johnson (Dave) would later play Quicksilver in the Avengers film series.
Katie says she reads comics such as Shojo Beat, which is actually a manga magazine published by Viz Media from July 2005 to July 2009.
Nicolas Cage (Damon Macready) and Lyndsy Fonseca (Katie Deauxma) share the same birthday (January 7).
The background music heard as Hit Girl rescues Big Daddy and Kick-Ass is Strobe (Adagio in D Minor). A similar background music track was used in Danny Boyle's film Sunshine (2007). John Murphy composed the music for both films. Mark Strong, who plays Frank D'Amico in Kick-Ass, appeared in Sunshine.
Clark Duke (Marty) and Lyndsy Fonseca (Katie Deauxma) also appeared in Hot Tub Time Machine (2010).
In one scene, Katie mentions the Scott Pilgrim comics to Dave. The film adaptation, Scott Pilgrim vs. the World (2010), starred Michael Cera. Cera had previously appeared with Christopher Mintz-Plasse (Red Mist) in Superbad (2007) and Year One (2009).