Esoteric Happy Ending: Prince John is banished in the end but he will become King of England upon Richard's death and his reign will be the beginning of the end of the Angevin Empire.
Fair for Its Day: Marian is the one who comes up with the plan to rescue Robin. A female being credited with a plan to rescue a male was rather progressive for 1938.
Foe Yay: Robin's duel with Guy sizzles with homoeroticism, with plenty of thrusting, sweating and panting and moaning in each other's faces.
Genre Turning Point: Before this film, historical movies tended to be written with a ton of Purple Prose. The original script was reportedly one of the worst cases of it ever, and was totally rewritten with more natural-sounding dialogue, leading to the practice being very quickly abandoned once its success became clear.
Tough Act to Follow: For many this is the definitive film version of Robin Hood... Unless it is a portrayal in a film adaptation of Ivanhoe.
What an Idiot!: Marian's attempts to hide the fact that she is trying to warn the King are ... less than convincing. She writes a letter to King Richard, telling him of the assassination plot and then hears a knock on her bedroom door. Despite the fact that there is a) a lady's maid next to her who successfully hides and b) a fire burning on the hearth right behind her, she neither gives the letter to the maid nor throws it in the fire, nor does she seek a delay with the obvious "I'm getting dressed!" or somesuch. Instead she puts it in a conspicuous box on a table that she claps shut and still has her hands on when Sir Guy bursts through the door, and that she stares at while he toys with it.
Hollywood Homely: In the episode, "A Husband For Marian", Marian's servant is described as "the homeliest woman in Britain". While certainly no Marian, the woman is rather nice looking in a plain sort of way.