From TV GUIDE 31 March 1956:

"Sign In, Please! - Wild adventures of six hectic years on "What's My Line?"

Written by Frank DeBlois

A couple of months ago, What's My line? observed it's sixth anniversary on TV. During this span, more than 300 "mystery guests," ranging from United States senators to talking mules have sought to baffle its panel.

Only once in 312 performances, executive producer Gil Fates recalls, did the mystery guest fail to appear. The culprit was Denise Darcel, who, through no fault of her own, became involved in a blizzard in Connecticut. Three minutes before show time, Fates learned that Denise couldn't make it.

"That night," he says, "I was almost a dead man. I even remember that I looked longingly out the window at the sidewalk 20 floors below. How tempting it seemed! Then, suddenly, I began to hear sweet music - and it didn't come from heavenly harps."

It came, indeed, from a network orchestra bleating out the finale to a CBS-TV show called Celebrity Time, which was just going off the air in the studio next door. Wild-eyed, Fates dashed into the hall, collared Celebrity's host, Conrad Nagel, and rushed him into What's My Line? just as emcee John Daly had begun to grope around for Denise.

One of the worst crises, Fates recalls, took place the night Arthur Godfrey completely forgot he was supposed to appear.

On the vital Sunday, Arthur went home, took off his clothes, took a warm shower, then stretched out on the couch to look at his TV set.

"Stay around," he heard the announcer say at the conclusion of a program, "for What's My Line?"

"Heavens!" hollered Arthur. "I'm supposed to be on that show now!"

He jumped up, pulled on his pants and took off. He arrived just as Fates was about to go into his 20-floor dive.

During the Neanderthal years of TV it was almost impossible to get "name" personalities to appear on Line. Hollywood stars took a bleak view of television, and Broadway personalities considered TV a cut above Sammy's Bowery Follies.

Today it is different. With What's My Line? one of the top panel shows on the air, neither Fates nor his employers, Mark Goodson and Bill Todman, need worry about cajoling guests.

The rules for a guest's eligibility are rudimentary. He must be familiar enough for viewers to recognize him by face or name. Therefore, Fates leans heavily toward the entertainment world. He has found, to his chagrin, that poets, statesmen, industrial tycoons and mahjong champions are often less well-known than TV stars, baseball players and talking mules.

Mystery guests who baffled the panel included Rosalind Russell (she had laryngitis and everyone thought she was a man), Eddie Fisher (Dorothy Kilgallen insisted he was Vic Damone) and Jules Montenier (the program's sponsor).

But, despite occasional strike-outs, the panel's batting average is high (about .900 according to Fates). Dorothy Kilgallen (who is the only original panelist left) is the champion mystery-guest guesser, with Bennett Cerf a close runner-up. Arlene Francis finishes a good-natured third, and Fred Allen, a relative newcomer, is ensconced in the cellar.

Guests get few instructions from Fates. They are advised to disguise their voices by grunting, groaning, simpering or affecting an accent. Edward G. Robinson used an Irish brogue and was identified almost immediately. Fredric March employed seven separate accents, hoodwinking the panel completely. Jayne Mansfield disguised everything but her plunging neckline and Kim Novak tried merely smiling.

Although mystery guests are protected from the panel by elaborate security measures, there have been some classic slip-ups. One week Samuel Goldwyn was scheduled as a guest. He was met at LaGuardia Field by Dorothy Kilgallen and innocently confessed that he was appearing on Line. That night he dined with Bennett Cerf.

"Bennett," he confided, "what a dope I am! Today I told Dorothy I was going to be on your show."

Result - both Dorothy and Bennett disqualified themselves as panelists.

Ginger Rogers played it cute. Scheduled as a mystery guest, she dined with Cerf the night of the show. After dinner she yawned, stretched, and said she was sleepy. After Bennett dropped her off at her hotel, Ginger hopped a cab, passed his car and was hiding backstage when he arrived.

One guest who will never be asked to repeat is Francis the Talking Mule.

Francis made his now celebrated appearance as a mystery guest last year. In order to baffle the panel, the happy hybrid's hoofs were swathed in burlap. It was a brilliant stratagem - and a miserable failure.

"The wind shifted," says Fates," and gave him away."