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.
“My goal? To test out every diet and exercise regimen on planet earth and figure out which work best. I sweated, I cooked, I learned to pole dance. In the end, I lost weight, lowered my cholesterol and doubled my energy level. I feel better than I ever have.”