Look at the Coen brothers. All their minor characters are as interesting as their protagonists. If the smaller characters are well-written, the whole world of the film becomes enriched. It's not the size of the thing, but the detail.
“Ideas improve. The meaning of words participates in the improvement. Plagiarism is necessary. Progress implies it. It embraces an author's phrase, makes use of his expressions, erases a false idea, and replaces it with the right idea.”
“That's the trouble with being me. At this point, nobody gives a damn what my problem is. I could literally have a tumor on the side of my head and they'd be like, 'Yeah, big deal. I'd eat a tumor every morning for the kinda money you're pulling down.'”