Jane Goldman one of the screenwriters, said that when she works with Vaughn she does the "construction work" and the "interior designing" while Vaughn acts as the "architect."
Filming locations include Hamilton, Ontario, Canada; Dip 'N' Sip Donuts on Kingston Road in Toronto, Sir Winston Churchill Secondary Schooland "many Toronto landmarks that play cameos"; and various locations in the UK, including Elstree Studios. The opening sequence with Nicolas Cage was filmed in a sewage plant in East London.
The 2D/3D animated comic book sequence in the film took almost two years to finish. Romita created the pencils, Tom Palmer did the inks, and Dean White did the colours.
Good source of information: http://www.scribd.com/doc/42700167/Kick-Ass-Production-Notes