Novels: You get the words and only the words to describe scene, character motivation, dialogue, etc. Basically, novels have to cover everything and be complete in and of itself.
Screenplays/Plays: Are not complete until they are performed. Often, not until after weeks and weeks of rehearsal/shooting. Russell Crowe was reportedly pissed that Gladiator was being written while they were still working on it--and before you say, "Well, Crowe gets pissed at a lot," let me say in his defense that it makes an actor's job harder when they don't get to interpret something whole.
Wodehouse wrote musicals and plays and his work has been adapted for the screen. But, as mentioned, the screen works differently than prose. You'll be pleased to know that the two actors who portrayed Jeeves and Wooster in the British series based off of Wodehouse's two legendary characters, the legendary-in-their-own-right Stephen Fry and Hugh Laurie, took the adaptation seriously.
Stephen Fry even wrote an essay on it. Check it out in whole here.
In the essay, Fry says, "When Hugh Laurie and I had the extreme honour and terrifying responsibility of being asked to play Bertie Wooster and Jeeves in a series of television adaptations, we were aware of one huge problem. Wodehouse's three great achievements are plot, character and language, and the greatest of these, by far, is language. If we were reasonably competent, then all of us concerned in the television version could go some way towards conveying a fair sense of the narrative of the stories and revealing, too, a good deal of the nature of their characters. The language, however, lives and breathes in its written, printed form."
Then he gives an example at random. But I'm not going to do that. Let's take a peek at Jeeves disapproving of some outfit or other of Wooster's in "Leave it to Jeeves":
"I remember meeting Monty Byng in Bond Street one morning, looking the last word in a grey check suit, and I felt I should never be happy till I had one like it.
'Jeeves,' I said that evening, 'I'm getting a check suit like that one of Mr. Byng's.'
'Injudicious, sir,' he said firmly. 'It will not become you.'
'What absolute rot! It's the soundest thing I've struck for years.'
'Unsuitable for you, sir.'
Well, the long and short of it was that the confounded thing came home, and I put it on, and when I caught sight of myself in the glass I nearly swooned. Jeeves was perfectly right. I looked a cross between a music-hall comedian and a cheap bookie.'"
Ah, now. We have a very clear picture in our heads of what Wooster looks like, we have a very good impression of Jeeves's opinion, and we have a very good idea of what these characters sound like. Enough verys, right? The scene is complete on the page.
Now, I don't have the teleplay in front of me, but it would look something like this (forgive me, trying to write a screenplay format in a blog is tricky):
Grey check suit arrives. Wooster pulls it out of box.
A check suit, just like Mr. Byng's.
Injudicious, sir. It will not become you.
What absolute rot! It's the soundest thing I've struck for years.
Unsuitable for you, sir.
Wooster ignores Jeeves. Puts on suit. Looks like cheap bookie.
In order for this scene to work, the suit has to be right there, so that the audience can see and react to it at the same time as Jeeves and Wooster. (Don't forget that television and movies are entirely visual media...whatever the writer wants the audience to see, they have to literally write a picture.) There's also no explanation to develop Wooster and Jeeves as characters.
The actors have to fill in the gaps to physically express what's meant, costumers have to provide clues to the station of the two men speaking, set designers have to establish the well-to-do apartment, and cameramen have to take the pictures that will be put together in a sequence that will make sense when watched. Plus, you know, everyone else who is involved in a production. That's just the tip of the iceberg.
To see the various ways that the crew of Jeeves and Wooster accomplished all of this, check out this YouTube video. (Sorry guys, copyright and all. They won't let me embed.)
And, since Stephen Fry still says everything much better than myself, I leave you with his words on the matter of page vs. screen:
"Well, try as hard as actors might, such an exchange will always work best on the page. It may still be amusing when delivered as dramatic dialogue, but no actors are as good as the actors we each of us carry in our head. And that is the point, really: one of the gorgeous privileges of reading PG Wodehouse is that he makes us feel better about ourselves because we derive a sense of personal satisfaction from the laughter mutually created. Every comma, every "sir", every "what?" is something we make work in the act of reading."