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.
“The rate of population growth in the United States is slightly below that required to reproduce itself.”
“I don't think anybody should ever take their life for being bullied. But if it wasn't for my family... and my circle of friends, I could definitely see why someone would see it doesn't get any better than this, but it does. Life is so beautiful.”