In the film Mark Hamill plays Professor Arnold, who is one of the central figures who joins Valentine in his quest to purge humanity and join him in his new world. In the graphic novel from which the film is based, the villain is only kidnapping celebrities to join him in his new world. Mark Hamill happened to be one of the celebrities being kidnapped by the villain.
The film's art and set direction was inspired and influenced by long-time James Bond franchise art director and production designer Ken Adam. Given the film's Bondian influences, Kingsman: The Secret Service (2014) production designer Paul Kirby embraced the opportunity to give a nod to famed production designer Ken Adam, who worked on many of the early James Bond films. Kirby has said: "We made something with its own sensibility but there are one or two subtle nods to acknowledge Ken's body of work. There's not a designer in the world that isn't a fan of his". Kirby has worked on three James Bond films himself, and all Pierce Brosnan Bond films, they being GoldenEye (1995), Die Another Day (2002) and Tomorrow Never Dies (1997).
In the first test, most of the recruits save themselves by rigging a snorkel through the toilets. While this might work if they were trying to avoid being gassed, a toilet flushes when the amount of water in the bowl exceeds the air pressure behind the curve in the commode. With the room the toilet is in full of water, the toilets would have been in constant flush mode and the pipe would have been full of water, making it impossible to get air through the 'snorkels'.
When Eggsy is in the police station and says he wants to exercise his right to a phone call, in the wide two shot there is no phone on the table, however when it cuts to the medium wide shot of Eggsy he picks up a phone which was supposedly there the entire time.
When Eggsy is running from security in Valentine's base, he is holding a gun in one of the initial shots despite being unarmed when entering. He does not actually obtain a handgun until he disarms a guard later on.