S9, E21: Ross is in agony because brilliant, beautiful professor Charlie (recurring guest star Aisha Tyler)--who usually prefers paleontologists--is instead dating shallow Joey. Nevertheless, Ross helps the desperate Joey pretend to be intelligent to impress Charlie--with mixed results. Meanwhile, Chandler and Monica's nervous visit to a fertility clinic is made even more uncomfortable by the unexpected appearance of Chandler's annoying ex-girlfriend, Janice (recurring guest star Maggie Wheeler). And Rachel argues with Phoebe over a corporate-owned spa chain that Phoebe detests.