Stalag 17 is the Billy Wilder movie which won William Holden the Academy Award that he should have won for his previous Billy Wilder movie, Sunset Boulevard.
So, y'know, pretty good film.
And the thing is, the character of Sgt. Sefton (Stalag 17) is built out of many of the same parts as Joe Gillis in Sunset Boulevard: cynical, selfish, smarter than almost everyone else in the room and ruthlessly practical.
It speaks volumes about Wilder's view of the movie business that, in Hollywood, these traits land his protagonist face down dead in Norma Desmond's swimming pool, while in a German POW camp, they might just make him a reluctant hero.