Revealing mistake: When Elly is "skating" on the black oil while fighting the bad guys, we can see that it is Bryce Dallas Howard's stunt double in a few shots where it briefly shows her face.
Continuity mistake: After they dance, Argylle gives his gun to LaGrange, who bends her arm and points the gun upwards. From the angle shot from behind, her arm is lowered.
Continuity mistake: When Lagrange finishes dancing with Argylle, she places both hands around his back, the left over the right. A shot later, they're placed the opposite way. (00:02:10)
Trivia: Chip, who plays the role of Alfie (Ellie's cat), is the pet cat of Claudia Schiffer, the wife of the film's director, Matthew Vaughn.
Trivia: Stay until the end of the movie. There is an extra scene involving the Kingsman bar after the credits.
