Charles Dickens' family did, indeed, keep a pet raven, which died unexpectedly while the family was away. Dickens told this story to another author - Edgar Allan Poe - who was then inspired to write a poem about a raven.
At 87 years old, Christopher Plummer was the oldest actor to ever play Scrooge. In fact, Scrooge is apparently elderly in the book, while in previous films, Scrooge is played by various middle-aged actors.
Filming took place mostly in Ireland, and some sets which had been used for Penny Dreadful (2014) were used for the production.
The booklet Dickens borrows from Tara the maid, "Varney The Vampire or The Feast of Blood", is a real Gothic novel written between 1845 and 1846 by James Malcolm Rymer and Thomas Peckett Prest. The novel was written in a format of monthly weekly deliveries, one penny apiece pamphlets, usually containing cheap horror literature, so each was commonly known as a "penny dreadful". This can be a nod to the fact that the movie was filmed in the same sound stages as Showtime's Penny Dreadful (2014).
Before Charles lands on "Marley" to be the name of Scrooge's ex-partner, he reads out a few other surnames that would eventually be used in later Charles Dickens stories: "Clennam" from Little Dorrit, "Heep" from David Copperfield, "Hexam" from Our Mutual Friend and "Magwitch" from Great Expectations.