The character actor in a movie typically isn’t the star. Not only are they a supporting character but they are the glue that keeps the movie from being boring. However most movies would not survive without them. They provide depth the the movie. (They are usually my favorite characters.)
Create one for your fiction project. Write an essay about one. Develop a poem around the premise.
Play with it. Try some stuff. Think about your favorite character actors and your writing. Make something happen.
Trust me it will be amazing as long as you have fun with it!