Comedies are always in demand, especially in the realm of screenplays. Even serious novels benefit from the occasional lighter touch to vary the tone.
How do you come up with a good comedy or a good comedy subplot? Here's what actor/writer Jason Segal said about that:
“The best way to write a comedy script is to write a drama. I’m not joking. That was the first advice I got from Judd Apatow, and I think that’s why his movies are so brilliant. He told me when I was writing Sarah Marshall, that the first draft he wanted from me was a drama. He said, ‘We’ll make it funny, it’s going to be funny because we’re funny, and we’re going to add jokes, and the cast will be funny — but the people will see it and keep seeing it and connect to it because it’s a drama.’"
That's the same thing comedy writing master Danny Simon taught me years ago, and I've followed that advice ever since. Make it real first, then find the funny. The person who taught Danny that was veteran comedian Sid Caesar (look him up).
Of course you don't have to write the whole script or novel as a drama, you just need to work out a storyline that works dramatically. Then the attitudes of your characters will make it funny. Nobody outside of the business will understand this. They think you have to start with the jokes. Big mistake!
(For friendly and helpful guidance on writing your novel or screenplay, see my book, Your Writing Coach, published by Nicholas Brealey and available from Amazon or your other favorite bookseller.)