Who is Fezziwig?

Mr. Fezziwig is a character in Charles Dickens's A Christmas Carol. We're introduced to him as Scrooge travels back in time with the Ghost of Christmas Past.
Fezziwig is Scrooge's former boss, and he's essentially the antithesis of Scrooge. While modern-day Scrooge is mean and miserly, Fezziwig is jolly and generous, as evidenced by the raucous party he throws for Scrooge and all the other local apprentices. He isn't too cool to bust out a few dance moves at said party, either.
While Scrooge is lonely and bitter, Fezziwig is very happily married. As the man who trained Scrooge, we can assume he's pretty good at his job, too, proving that it is possible to work hard, be good at your job, and not be a wretched person.
Because of their stark character differences, Fezziwig acts as Scrooge's foil in A Christmas Carol. That means that he reinforces Scrooge's character traits by being the opposite of them. By associating with someone as jovial, kind, and generous as Fezziwig, Scrooge only looks more miserable and greedy.