Scrooge Trolling Bob Cratchet after his Heel-Face Turn, which many actors have had a lot of fun with.
During this scene in the 1999 version, Bob is so (understandably) freaked out by Scrooge's actions that he actually grabs the fire poker to defend himself, just in case.
Fred wishing Scrooge a Merry Christmas and a Happy New Year.
Marley's Ghost tells Scrooge that he has sat, unseen, beside him many times. When Scrooge is understandably creeped out by this, Marley basically says, "It's no picnic for me either, bud."
"Tight as your Uncle Scrooge's purse strings"
Scrooge (in the 1986 version), who watched the simile games with the Ghost of Christmas Present, telling Janet the answer "To tight as" is "a drum". This troper thinks it would be funny taken Up to Eleven if he had that simile and forgot.
In a Crosses the Line Twice kind of way, the fact that Mrs. Dibley (Scrooge's maid) stole Scrooge's bed-curtain's, sheets, and his shirt. While he's still laying there, dead.
In the 2009 version, the second thing Scrooge does after waking up from his experience (the first being buying the prize turkey for Crachit) is wish his maid a Merry Christmas. She reacts as though he's lost his mind.