I've written before about how much I'm influenced by movies (and radio drama), but like everything else there are dangers. Novels are not movies (though there are connections and similarities).
Shepherd Book was a character in the TV show Firefly. He was a preacher ("Shepherd" is a title), and he came on the ship Serenity as a passenger. He had left the abbey where he had been living, and he was apparently eager to travel and see the universe again.
He boarded the ship as a passenger, and he just stayed through the rest of the series, somewhere between a passenger and a crew member.
He turned out to have a lot of knowledge of the criminal world – both its methods and its inhabitants. He also had a lot of knowledge of the government, including its covert operations, and he carried an ID card that got him immediate medical assistance from a government facility when he was shot. And he was obviously very experienced with firearms.
None of this was ever explained (though the other characters certainly did ask). In the movie Serenity, the captain says that Book has to explain how he knows so much.
"No. I don't," was his reply.
This would be very problematic in a novel. Too much unexplained (and almost always convenient) knowledge, too many disparate character elements. Not that you have to explain everything that your characters know, as I've written about before, but you do have to explain some things, and the more incongruous the elements are the more you might want to consider explaining them.
On the show, though, the character works just fine (and better than fine – Book is a wonderful character). But the writers of Firefly had one advantage that novelists don't have: Ron Glass, the actor who played Shepherd Book. Glass made the character work and seemed to be having a great time doing it.
I don't say this as a criticism of the show's writers, by the way. They knew who they were writing for (the great advantage of writing episodic television) and they knew what he could do. But people who write on paper (or in pixels) don't have that, so we have to do things a bit differently.