Office hours, explaining complex theories, assigning absurd amounts of reading every night, and don’t forget pop quizzes — this is the job of a college professor. College professors can either make your time in college a great one, or not so great. But imagine taking a class with a celebrity professor. For some people, that's a reality. Here are seven celebrities who are or have been college professors:Oprah Winfrey co-taught a leadership class at Northwestern. For a short stint starting in the late '90s, Oprah taught at Northwestern University's Kellogg Graduate School of Management.