Paper Lion (1968)

George Plimpton wants to write a story for Sports Illustrated on what it is like to be a quarterback for an NFL team. No one is willing to allow a klutzy amateur to go on the field for fear he'll kill himself. After several teams turn him down, Plimpton got the Detroit Lions to let him go to training camp. He tries to keep his true identity a secret from the real players. This is based on a true incident and many of the players play themselves in the movie.