I reference folk music, both traditional and contemporary. Child Ballads are good, because there's a lot of supernatural characters and a ton of Robin Hood and Knights of the Round Table stories.

Then on the plain, these champions met, a grisly sight to see
There were three feet between their brows, their shoulders were yards three
You'll open the gates, cried Jock o' North, you'll open them at my call,
And with his foot he has drave in three full yards o' the wall
I've used sea songs as the basis for adventures set on ships in particular. Everyone likes pirates, dastardly captains, and pissed-off sea monsters.

He's bade them return to old Ireland once more
Or broadside and broadside upon them would pour
This brave Irish hero has made this reply
We will never surrender, We'll conquer or die!

So it's broadside and broadside on each other did pour
And louder and louder the cannons did roar
This brave Irish hero has gained victory
Hurrah for true lovers - may they always run free!
War songs work too. The battle of Otterburn (1388) is a good basis for the classic siege/parley/duel thing.

Up did speak proud Percy there, and oh but he spake high
I am the lord of this castle, my wife's the lady gay
If thou art the lord of this castle, sae well it pleases me
For ere I cross the Border fells, the ane of us shall dee.
Even protest songs can work, as a start for a peasant rebellion. Will the PCs support it, put it down, or just watch the disaster unfold? It's like adding a historical event to your world. It could be the game-world's background; perhaps the king was murdered, or his daughter stolen by the fairies, long ago. Or perhaps the people are downtrodden under the lawful-evil king and his ministers and knights.
We work, we eat together, we need no swords
We will not bow to the masters or pay rent to the lords
Still we are free, though we are poor,
You Diggers all, stand up for glory, stand up now

From the men of property, the orders came
They sent hired men and troopers to wipe out the Diggers' claim
Tear down their cottages, destroy their corn
They were dispersed, but still the vision lingers on
Many songs are about ghosts. Many, many songs are about murder. Many have talking animals, people in disguise (often as the other sex), trickery, and much more. So much inspiration!