The storybook horse is an annual Kentucky Derby story.

A few, like the burnt-out Bidson in 1976 and the ridgling Rae Jet in 1969, actually made it through the race. Those two had something in common. Each finished a distinct last, Bidson at 72-1 and Rae Jet at 70-1.

The footnotes to Derby history say, briefly: "Bidson was without speed" and "Rae Jet soon lost contact with the field."

But the real Cindefellas never quite get here. Or, if they do, something invariably goes wrong a few days before the race. Like One-Eyed Tom in 1972. He was well-named, having lost an eye when turned out to die on the Nevada desert, only to wind up here for the Derby. Just one thing kept Tom from beating Riva Ridge that spring. He made a U-turn in his trial out of the starting gate.

Then there was Gift Silver, in 1952, owned by an elderly couple from Iowa. The Gift horst threw his exercise boy so often that trainers eventually convinced the Churchill Downs management the horse would be a menace to any 3-year-old that competed.

More often than not, however, the storybook horse never quite gets to Louisville. Annabelle, in 1968, was well-intended even though she would have been the first filly to compete in the Downs' famous feature since Solver Spoon in 1959.

Annabelle's owners decided to hold a fund-raising party in Toronto so that she could make the trip even if she couldn't ger the (mile and quarter) route. The party was considered a great success. Unfortunately, the owners spent so much money for the Mint Julips and other beverages that all the finds raised were needed to pay the party bill.

This year, Playboy Tony might have made good copy here, of . . .

The Playboy is owned, trained and was bred by Camille Cestare, an X-ray technician in Phoenix. Cestare always dreamed of seeing her colors carried in the Derby. If only Tony could have won an Arizona breeders' stkes at Turf Paradise to earn shipping money to the Downs. But Playboy Tony stayed out too late the night before the race and finished fourth, thus depriving the Derby of a rabbit - or would it have been a bunny? - for the early furlong.

There is, however, a charismatic colt in this year's probable Derby lineup. His name is Esops Foibles.

Last year, Esops Foibles won but one of nine stars. Affirmed beat him by lengths in the Hollywood Juvenile. He was going nowhere in a hurry until the distances lengthened this season. In his last two races, the Nashua colt captured the Lousiana and Arkansas derbies over 11/8 miles. He is currently the fifth or sixth choice for the Derby here May 6, depending on how fares today at Churchill Downs in the one-mile Stepping Stone Purse.

Six horses are entered in the Stepping Stone, including Ten Yard Penalty, Batonnier and Hoist The Silver. These three are on trial. Their appearance in the Derby probably will hinge on how they run today.

Batonnier was third in the Louisiana Derby.Ten Yard Penalty finished fourth, thrown offside by Alydar, in the Florida Derby. Hoist The Silver ran third in the California Derby. Silver is owned by Jack Dasso, a chiropractor from Sunnyside, Wash., who is president of Yakima Meadows Racetrack; Perry Levinson, a meat-packer from Seattle; Donald Golub, a Sunnyside (Wash.) farmer, and Elias Solomon, a retired banker from Mercer Island, Wash.

Such ownership from the Pacific Northwest undoubtedly are spurred on by the thought that a colt named Seattle Slew, owned by a White Swan, Wash., lumber family, captured the 1977 Derby and Tripple Crown.

A field of 10 is taking shape for his year's Derby.

"I wish the race was two miles," Jerry Frankel, owner of Espos Foibles, said recently. "I know my horse wants to go long. At the end of the races in New Orleans and Hot Springs, he was still going strong."

Frankel owns the Jerrell Co., which manufactures women's clothing in Dallas. Esops Foibles is named for the firm's Employees Stock Option Plan and for the Ribot mare who foaled him - Checkered Career.

"I don't know if we can beat the top horses or not. This is a terribly tough Derby," young trainer Lauren Ratelle admitted at the barn yesterday morning. "The fact we are going to lay out of it should help. Sensitive Prince, Affirmed and Believe It promise to make things happen early. Then Alydar will be coming along and then, hopefully, Esops Foibles."

Chris McCarron, the leading rider on the Maryland circuit the last few years, has the mount on Esops Foibles. Certainly, the owner, the trainer and jockey need no apology for being here.Esops Foibles has respectable Derby credentials even though the horse's name indicates he might be galloping through Wonderland.

Also, Esops Foibles will have available the veternary services of Alex Harthill. "Take him to Harthill" has long been sound advice. The vet has the reputation of knowing what a Derby runner needs, and seeing to it that he gets it.