P.O. Crean

Not very much, this is mostly a factor of being based on Huntford's book, Huntford focused almost entirely on Scott, the winter's journey is also absent and the Northern party is barely touched. Griffiths did write Evans' rescue into the Screenplay (Judgement Over the Dead), but those scenes weren't filmed (not enough money).

Huntford would write a bit more of Crean in his Shackleton Biography, which is more than the Kenneth Branaugh film did. Part of Crean's comparitive invisibility is he didn't write much (Lashly was the only lower-deck man to do much writing at all).

But really, you could make a good scene (for the next Endurance Film) with Crean and Shackleton at the Endurance farewell party to tell you everything you need to know about the guy who'll be with him most of the movie. Have Shackleton tell the story to a group with the lady looking at his Polar medal (after rescuing a very awkward "officer" Crean, Finish with Fisher coming up and throwing out his (later) quote about how any fool can obey orders, then telling Shackles that while he doesn't need his men or ship, they are on their own (getting the Discovery home cost enough for a Battle Cruiser).