Dustin Hoffman based his character on the movie's screenwriter Dalton Trumbo, particularly his withdrawn and shy mannerisms which had inspired Hoffman when meeting Trumbo for the first time.
Although billed as a true story, the French in French Guiana claim that much of the story of Henri Charrière (Papillon) is fabricated. Papillon was documented to have been incarcerated in Saint Laurent and may have escaped from there, but he never served any time on the Devil's Islands (now known as Iles du Salut or Salvation Islands). The book and movie both present Devil's Island as having rocky cliffs, when in fact, though the entire island is rocky, it gently slopes into the surrounding sea.
"Papillon" is one of those rare films that were given two major releases by two different distributors. First, Allied Artists and then Columbia released it in 1973.
Once the prisoners arrive at the island and are walking with their bags, we see one prisoner fall over, onto a chicken. You can see the chicken get injured (probably a broken leg).