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.
“In soloing - as in other activities - it is far easier to start something than it is to finish it.”
“He told me he was working as an interpreter in a doctor's office in Brookline, Massachusetts, where I was living at the time, and he was translating for a doctor who had a number of Russian patients. On my way home, after running into him, I just heard this phrase in my head.”