I'm wondering if that's what my personal favoritest Writer of Fiction, Ed McBain, did. All of his characters, including his minor characters - no, especially his minor characters - were rivetingly interesting because he'd take your expectations and play with them in some way. People had their eccentricities, their foibles, their strange ways of perceiving the world, and even when all those details weren't brought onto the page, you could just sense the hints behind the words of a deeper, crazier world of people who could have stepped onto the stage from Real Life.
So, go on everyone ... come up with 5 unknown facts about your characters, major or minor, and see if that can have an impact, even if it just means that the minor character you see for a page is a little gentler and better-educated than the stereotypical truck driver.
Of course, there are limits: no need to do this for characters that have a three-line entry and exit. They're just setting details!