Summarize:

Use dialogue to add humour to a screenplay. Have witty back and forth between characters. Have one character who is full of funny one-liners. Create running jokes that are said throughout the screenplay by different characters. Dialogue gives you a chance to have your characters tell jokes to one another and be witty. For example, you may have one character who uses a signature catch phrase and tone of voice to say their dialogue, creating humor. Develop a character over a long period of a time in a novel so they become endearing, witty, and funny to the reader. Give them a funny childhood or a unique sense of humor. Let the character's voice and actions come through as the novel progresses and add in funny or amusing details about the character. The reader will then get a sense of humor from the character. For example, you may have a character who seems minor in the story but always has a funny aside. You may then have them become more important as the novel progresses, putting their humor front and center. The element of surprise can be a fun way to jolt your reader and make them laugh. Have a plot twist in the play that you find funny and surprising. Keep the viewer guessing and use the element of suspense to create surprise and laughter. For example, you may have a big reveal 3/4 of the way into the play where a character turns out to be a woman dressed as a man. You may stage the reveal so it is funny and surprising for your audience.
Emphasize comedy in screenwriting with dialogue. Use long-term character development in a comedic novel. Surprise the reader in a comedic play.