Ben Affleck was virtually blind, as he had to wear heavy-duty contact lenses, which blocked out most of his vision.
In their big fight scene, Jennifer Garner accidentally kicked Ben Affleck so hard in the head that he briefly blacked out.
As a fan of the character, Ben Affleck made a point of reading every single comic book that featured Daredevil, in preparation for the role. He also wrote the foreword of the collected paperback edition of Kevin Smith's run on the Daredevil comic book.
The film was originally envisioned as R-rated, with nudity and hard violence.
Stan Lee: (at around 13 mins) An elderly man that a young Matt Murdock stops from walking in the streets by holding out his walking stick in front of him. Lee's character is based around the elderly blind man from the comics which Matt saved, but also resulted in the accident that gave him his powers.
Frank Miller: (at around 59 mins) Graphic novelist, former Daredevil writer, and creator of Elektra, is quickly shown dead as Bullseye pulls away on his stolen motorcycle.
Claudine Farrell: (at around 29 mins) The woman on the answering machine is Colin Farrell's sister and on-set assistant, who also appears in the pub scene when Bullseye is introduced.
Kevin Smith: (at around 1h 7 mins) Kirby the lab assistant. Smith wrote two acclaimed comics for the hero, "Guardian Devil" and "Daredevil/Bullseye: The Target". The character is named after the legendary Jack Kirby, who illustrated many of Stan Lee's comics during the 1960s, although Jack Kirby's work on Daredevil was mostly limited to the cover illustrations.