Many minor characters in the film are played by themselves, including most of the medical professionals, who re-enacted the real events in unscripted scenes. Dr. Jeffrey Kalish removes the bandages from Jake Gyllenhaal's legs just as he had from Jeff Bauman's, and five members of the Martino family play themselves at United Prosthetics. Others include the rehab techs and nurses at Spalding Rehab, and first responder Jerry Kissel.
Jeff Bauman's former supervisor at Costco, Kevin, auditioned to play himself in the movie. Although he was not chosen for the part, he is an extra in more than one scene.
Both Jeff Bauman and Jake Gyllenhaal threw out the ceremonial first pitch at Fenway Park for the Marathon Monday game of April 18, 2016.
Filmed at the same time as Patriots Day (2016), the other Boston Marathon bombing-related movie. Jeff Bauman is a supporting character in it portrayed by Dan Whelton.
Comedian Lenny Clarke actually knew the character he played, Uncle Bob, who was a huge fan who had been to many of his shows.