I'm sorry, but we cannot write this for you -- what we can do is to give you some ideas that will help you do your own work.
Surely, the first reaction of Bob Cratchit and Fred will be astonishment. You can talk about all the things that Scrooge has done in the past that would make this so amazing. Talk about how, for example, Scrooge scolded Fred so harshly just for stopping by to say Merry Christmas.
Next, I would speculate a bit about why this has happened. If someone you know changed so much so quickly, I would think that you would wonder how it could have happened. So you should try to make some guesses (from their perspective) as to what could have changed Scrooge's personality so dramatically.