From http://www.marylaine.com/exlibris/xlib107.html, "Being an Anomaly: Male Librarians," a phrase describing people who are unexpectedly
promoted in their job and pushed toward
management work whether they seek it or not, because of characteristics they can't control. Metaphorically, the employee can't see that they've stepped onto an upward path. (In this article, it referred to male
librarians, a
minority in the field, being expected to work in
administration rather than, say,
children's services.)
The opposite of "glass ceiling," which women have sometimes confronted in career fields where they are a minority.