Interact Theatre Company's "George--Don't Do That!" is warm and pleasant yet less than wonderful, but wonderful might be too much to expect from a revue that is equal parts biography and homage. The subject at hand is Joyce Grenfell, celebrated British comedian of stage and screen in the middle decades of this century, and the show that Catherine Flye has devised and stars in is a simple act of adoration.

If you don't know much about Grenfell--who died in 1979 after a fruitful, multifaceted career on both sides of the Atlantic--never fear. "George" is nothing if not informative: a narrator sits to the left of the small stage at Arena's Old Vat Theater providing factual data (Roger Mudd, in black tie, did the honors for Friday's opening night; a variety of guests will narrate throughout the run). The stage proper belongs to Flye, who makes her entrance as Grenfell from the darkness of the audience, as if the ghost of the great star were being coaxed back into the theater once more.

"I like life!" Flye/Grenfell sings in the opening number, accompanied on piano by Alex Hassan. As the narrator methodically charts Grenfell's life and career, Flye (always as Grenfell or one of Grenfell's creations, pulling costumes off a rack at the back of the stage) reads letters, sings songs that Grenfell penned with composer Richard Addinsell, and plays some of the closely observed, quirky characters from Grenfell's gallery.

The show's title, in fact, comes from the signature line in a classic sketch about a harried nursery school teacher whose duties slip down the slope from basic instruction to crisis management. One unseen child has something in her nostril, another has a finger stuck in a keyhole, and every so often a look of horror crosses the teacher's face as she says, "George--don't do that!" The fact that George's chronic misdemeanors are left to the imagination makes them all the funnier.

Flye easily matches the sunniness at the core of Grenfell's comedy, and if the material sometimes lacks theatrical spark, the actress usually makes up for it in sparkle. As an unpolished Cockney lass giving an arts-and-crafts demonstration, for instance, Flye deliciously twists her lips around the phrase "empty beechnut husk clusters." And her musical comedy is a hoot: Flye's rendition of four separate encores, each sung by a different sort of character (the cross-eyed schoolgirl, the serious German lieder singer, etc.), is the funniest sequence all night. (The story of how Grenfell "discovered" a character while cleaning her teeth runs a close second.)

The show includes the odd serious or bittersweet bit; Grenfell, like many a comedian before and since, liked to play people as she observed them--in dark shades as well as light. But malice, we are told twice, was not part of her arsenal, and the unrelenting gentleness of the program has the effect of flattening things out.

Grenfell apparently heard this sort of criticism, as we learn in a letter discussing advice to make her performance "broader," "harder-hitting." Flye's text makes it clear that Grenfell would happily plead guilty to cheeriness and sentimentality, and the actress obviously stands in solidarity with her subject. The throwback charm of Grenfell's art works more often than not; no doubt Roger Mudd wasn't the only Flye-watcher in Friday's audience who spent most of the night with a grin on his face.

George--Don't Do That! Devised by Catherine Flye. Through Oct. 10 at Arena Stage's Old Vat Theater. Call 703-218-6500.

CAPTION: Catherine Flye as Joyce Grenfell in Interact's "George--Don't Do That!"