S4, E7: When Professor Bunt goes out of town to interview with his future brother-in-law for a teaching position at Harvard, he puts Charles in charge of entertaining his visiting sister Dodo (guest star Marcia Wallace) for the evening. Because he already has a commitment to Buddy, Charles talks Walter Powell, who never dates, into taking her out. Charles and Buddy return that night only to have Walter and Dodo announce that they are getting married.