What's My Line? Season 18 Episode 53

FINAL MYSTERY GUEST JOHN DALY - The final mystery guest was host John Daly himself. John signed in and took his seat. John alternated between a falsetto "guest" voice and his standard moderator voice, fooling the panel for a number of questions. He fliped the cards over all the way down to "6 down and 4 to go." Finally, Bennett Cerf asked, "Could Mr. Daly possibly be impersonating himself?" Bennett pegged him! John explains that the gimmick of using him as the mystery guest had been devised years earlier as backup plan in case the scheduled mystery guest didn't show up. He said that despite a few close calls, this never happened, so the producers decided to use this stunning trick for the final episode. - Suzanne (2004)