THE 1940s RADIO HOUR - At Arena Stage's Kreeger Theater through December 19.

When was the last time you saw rolled hair, padded shoulders and seamed stockings?

Oh. Just now, in the latest pictures from Paris.

Well, when was the last time you saw a spoof of an old radio station, complete with sound-effects man and smiley singers?

Last summer, in "Annie."

How about impressions of all those great entertainers of the 1940s, the kind they don't make any more?

You haven't seen this in "Paradise Alley" yet because it's only opening this weekend. Not that there's been any lack of 1940s routines on stage and screen lately.

"The 1940s Radio Hour" at Arena Stage's Kreeger Theater has a cast of padded-shoulders women and men wearing hats doing characters resembling Judy Garland, Frank Sinatra, Lena Horne and Rudy Vallee, in a spoof on 1940s radio. It may not have come along to fill a cultural void, but it is funny.

A bouncy, peppy group with a lot of smart-ass naivete assembles to put on a 90-minute radio variety hour, consisting of renditions of "Blue Moon" and "Pepsi Cola Hits the Spot," show-biz patriotism such as assurances of fidelity from a blonde singer to the boys at war and a tap dance done in an abbreviated Uncle Sam costume, and a mini-dramatization, in stage English accents, of Dickens' "A Christmas Carol."

In the background, little hopes, failures and flirtations are carried out-nothing that would constitute anything so grand as an actual plot, but enough to keep a thread of interest going.

Walton Jones' play is not witty. Its one attempt at ture satire - recreating a breakfast-show routine from that period and then giving a period takeoff of it - is weak. But it produces a steady, gentle sense of fun by going through the show-business conventions of the time as they were actually done. The recognition factor will make it amusing for people who remember, and for those who weren't around the amusement is viewing the past as innocent because one never happened to be caught up in its fashions.

The unpatronizing spiritedness of the actors - Donna Drake, Jeff Keller, John Doolittle, Kimberly Farr, Franchelle Stewart Dorn, Jack Hallett and others, including Jane Bloom puffing her life into the saxophone in the band - is utterly engaging. David Lloyd Gropman's studio set, complete with Coke machine and flashing applause sign, and William Ivey Long's costumes, the authentically sleazier versions of what is being shown in Paris now, achieve the camp through literalness.

One wonders, of course, what the future theater will do for revivals of this period, which seems to consist of nothing but revivals of other periods. In the same building, at Arena's main theater, the Vienna of just a few years previous to this play is being done.

That makes an interesting contrast. With all the cynical, iron piggishness being exhibited in "Tales From the Vienna Woods," and all the goofy simplicity epitomizing American in "The 1940s Radio Hour," how is it, again, that we managed to win the war?