Wow. I did not know this about The Two Towers.

There’s a scene in The Two Towers where a Rohirrim flag pops off of its flagpole just as Aragorn, Gandalf, Gimli, and Legolas come riding up to Edoras.  It’s one of my favorite scenes in the movie, in fact, because it so concisely evokes the problems Rohan is having at that moment.  And it was completely accidental! Peter Jackson simply ran with it, because when the universe gives you a crit like that you take it.

Remember: if it was an accident that rebounds in your favor, you look people right in the eye and say I meant to do that.  This is the First Law of the Bard.