Final answer:
Scrooge expresses nostalgia and a deep appreciation for Fezziwig's generosity, leading him to reflect on and regret his own lack of kindness and warmth in the past.
Step-by-step explanation:
When Scrooge exclaims, "Oh, my dear, dear...Fezziwig, alive again!" in Scene 5, paragraphs 48-59, he is expressing nostalgia for his past, specifically the joyous Christmas celebrations hosted by his former employer, Fezziwig. This sentiment embodies Scrooge's realization of the contrast between the warmth and generosity of Fezziwig's character and the cold, miserly person he himself has become. Scrooge is reflecting on how Fezziwig's kindness greatly influenced his own life, and he is beginning to regret that he did not follow Fezziwig's example of generosity and hospitality through the years.