A ChangeAgent is someone who is irritating enough to cause an organization to change, but not so irritating that s/he gets thrown out.
After the good joke, we must understand that a ChangeAgent is:
9 tips for Change Agents. (From: http://www.fastcompany.com/online/05/changetips.html)
See TrainTheTrainer, http://home.att.net/~nickols/change.htm, ChangeYourOrganizationTactics