Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: The Muppet Christmas Carol
Every scene with the Ghost of Christmas Yet to Come.
Which is one of the reasons Gonzo and Rizzo abandon the narration till the finale. Partly, to let the scene play without comedy, but also because they were creeped out.
Even Gonzo assures the audience that they'll return in the finale. Thankfully, they do after Scrooge wakes up from his nightmare.
While the Ghost of Christmas Yet to Come is intentionally creepy, the child-like Ghost of Christmas Past is legitimate Nightmare Fuel.
Well she's not that bad in some scenes.
The scene where Jacob Marley's face appears on the door knocker and starts wailing at Scrooge.
The song the two of them sings is supremely creepy when you take the time to read the lyrics.
You're doomed for all time
Your future is a horror story
Written by your crime
Your chains are forged
By what you say and do
So, have your fun
When life is done
A nightmare waits for you
This adaptation also went all out with the chains; they not only appear out of nowhere at one point to constrict Scrooge, but at the end of the number they slither out from the darkness and slowly drag the Marleys into the shadows.
Before the Marleys appeared, Scrooge was enjoying his snack when the bell suddenly rang. He looked up, then heard a creak from the stairs. But thought nothing of it, until it rang again, this time a bit longer. After it stopped, the fire went out. When we see a luminous light from downstairs, along with an ominous chorus.