One thing that has bugged me for about twenty years now is that, when filmmakers adapt Hamlet, almost all of them end up cutting out Fortinbras entirely.
Granted, he's a character who only shows up in one scene, and has very few lines. He seems like an easy cut from a play that's over four hours long (even though he has the last line in the fucking play); but, if you dump Fortinbras, you basically have to dump the entire soul of Shakespeare's play.
Everybody knows "To be, or not to be." Yeah, that's a cool soliloquy; but, most people aren't as familiar with, "How all occasions do inform against me and spur my dull revenge." That's a crime against literature. Hamlet's act 4 scene 4 soliloquy comes after he's killed Polonius and he's being shipped off the England. Hamlet is happy to go and leave the whips and scorns behind him by act 4 scene 3. It's not until he speaks to Fortinbras's soldier about the impending invasion that Hamlet grows up, realizes that the world doesn't revolve around him, and decides to come back to Denmark and carry out his destiny.
If Fortinbras isn't a character in Hamlet, the most important moment in the story happens off screen and is, at best, implied. There's no "... while to my shame, I see the imminent death of twenty thousand men..." or "...Oh, from this time forth, my thoughts be bloody, or be nothing worth." if Fortinbras isn't there.
This is something that has bothered me for a long time. I don't know how people get millions of dollars to adapt this play while not understanding the narrative.