IT'S peculiarly satisfying to see a formal Victorian dinner party interrupted during the soup course by the arrival of a real live frog. After hopping under the table, the diminutive latecomer is gently retrieved by a butler, who "seats" him next to the painfully embarrassed young mistress of the house. From his perch on a stack of velvet cushions the frog proceeds to mingle in a delightfully froglike way, jumping into soupbowls and overturning wine glasses.

To her consternation, the young lady can't avoid or disown the unwelcome creature. She has admitted to her father that the frog did her a favor and that she offered him hospitality in return. Resolutely courteous, her father insists that she keep her word: "He who helped you when you were in trouble ought not afterwards to be despised." The girl's predicament unfolds with a dreamlike humorous logic: She's trapped in a drawing-room comedy nightmare, compelled to acknowledge a forgotten obligation that has suddenly become acutely public and humiliating.

This deft, subtly revealing sequence is the highlight of "The Frog King, or Faithful Henry," the third in a projected cycle of fairy-tale shorts directed by Tom Davenport, an independent filmmaker who has earned a modest but secure reputation while working out of his farmhouse in Delalane, Va. Made for about $16,000, "The Frog King" had its official Washington premiere last Sunday at a special children's matinee program at the American Film Institute Theater, sharing a bill with Davenport's previous adaptations from the Brothers Grimm, "Hansel and Gretel, an Appalachian Version" and "Rapunzel, Rapunzel." Since the AFI debut sold out, the program is being repeated today at 1:30 p.m. at the Biograph.

"The Frog King" runs 20 minutes, the earlier films 16 minutes each. Davenport will be on hand to introduce and discuss the movies, assisted by cast members Ann Clark and Michael Higgins and puppeteer Julian Yockum. A 13-year-old student at the Washington Ballet, Miss Clark plays the vexed heroine of "The Frog King." Higgins is the handsome, personable young suitor who eventually emerges from enchanted concealment in the form of a frog. Yockum manipulated the large puppet used in close-ups of the frog speaking his lines.

At a preview screening of "Hansel and Gretel" and "The Frog King" at Barcroft Elementary School in Arlington, a large juvenile audience, ages 5 to 8, seemed to find the display of this puppet as fascinating as the movies themselves. It was a magic prop that virtually every kid desired to touch or stroke, so the presentation at the Biograph will certainly be enhanced by the presence of both puppet and puppeteer.

Davenport and his wife, Mimi, who painted the frog puppet (designed by Tom and Susan Culnan) and supervises the distribution of her husband's films, have three sons. Davenport was inspired to branch out from strictly documentary filmmaking when their eldest, 9-year-old Robert, was hospitalized briefly in 1975. Recalling "Hansel and Gretel" from his own childhood, Davenport read it to his son in the hope that it might calm possible fears about being sick and spending time away from home. His boy's subsequent fondness for the story moved Davenport to film an admirably spare, evocative adaptation, with Hansel and Gretel transformed into the abandoned children of an impoverished Appalachian family, and then entertain the idea of a series of similar shorts.

"Rapunzel" doesn't quite find an appropriate tone, but "Hansel and Gretel" and now "The Frog King" certainly justify Davenport's aspirations. gThey also provide an entertaining contrast, since the mood of "Hansel and Gretel" is incisively ominous while the mood of "The Frog King" is playfully comic. The new film derives a considerable measure of appeal from the sheer kick of watching a frog disrupt a dinner party. Little kids in particular may feel keen gratification when he splashes merrily around the table without suffering unpleasant consequences. Grown-ups may feel more amused by the aplomb of Ernest Graves in the role of the host and by the implications of the heroine's discomfort, which wittily evokes a good deal of the social and erotic panic associated with adolescence. Ann Clark's "princess" resembles a schoolgirl forced to change her mind about an apparently intolerable boy: To her amazement the slimy creep is somehow changed into an attractive companion, even a love object.

Davenport falters only at the denouement, in part because he trusts the Grimm scenario more than he should. Ann Clark and Michael Higgins look so appealing together that the picture really cries out for a scene in which the newly revealed "king" endears himself to the astonished girl. Instead, the actors play in pantomime while a narrator (davenport himself) sums up by reading the fairy tale text. The misjudgment is magnified when the narrator goes on to mention the last-minute character of Henry, the king's faithful servant, but Davenport neglects to show us how the three iron bands around his heart have been freed in happiness at his master's return. Sturdy as these fables are in most respects, certain aspects need to be enhanced and others finessed.

Despite the closing slip-ups, "The Frog King" remains a charming piece of work, and I hope Davenport tries to enlarge on its humorous tendencies in subsequent movies.