Minor Characters in Fiction

We've talked a lot about main characters, but what about minor characters? Are they important? Do they need as much detail as the main characters?
Here's what we think...
Find Karin at:
/ authorkarinbeery
/ karinbeery
/ karinbeery
Find Pegg at:
/ pegg.thomas.author
/ pthomas_author
/ pegg_thomas

[@gloriav.4413]

Thank you!