Vlasta Krsek is a 50ish, suburban Chicago matron who bills herself, with typical modesty, as the "International Queen of the Polka." Her act is Vlasta and the Altar Boys. At one gig someone proclaimed her band "The Pink Floyd of the Polka." An unkind observer, in other words, might call her a walking Polish joke.

But wait a minute. Vlasta is Czech. For another thing, that was indeed Vlasta plugging in the mike for her accordion, twirling around in her century-old traditional costume and barreling through a rousing rendition of The Johnny Carson Polka recently on The Tonight Show.

Vlasta's showbiz career began in Central Europe in the late 1930s when, billed as "The Shirley Temple of Czechoslovakia," she starred in some 20 feature films. Emigrating to the U.S. after World War II with her mother and brother, Vlasta settled in Chicago, married her beau, Jan, at 16 and raised two children while working in an appliance factory. When the boss laid her off, Jan told her: "Vlasta, go do your dream." And do her dream she did, thanks to an ingenuous talent for self-promotion.

In 1979 she cut her first record: The Pope John Paul II Polka, in honor of the pontiff's visit to Chicago. Six years later she sent a copy of The Happy Birthday President Reagan Polka to the White House. When Reagan visited Chicago Heights last June, sure enough, she was invited to serenade the President.

When Vlasta saw that it was time "to bring polka out from the ethnic radios," she gave the world The Deejay Polka, which Steve Dahl, a wacky FM-radio personality, quickly adopted as his theme song. Dahl invited Vlasta to play at rock clubs, fronting his band Teenage Radiation.

Then came The Johnny Carson Polka.

Dubbing their campaign "Vlasta Aid," Chicago deejays Jeff Elliott and Jerry St. James urged listeners to write Carson's producers, who agreed to have Vlasta on after seeing a P.M. Magazine segment in which she said, "You can't get higher. That's my dream: to appear on Johnny Carson."

The reality was a payoff, says Vlasta, for all those years of "shlepping the bars, often playing for nothing, playing even flea markets." She's not one to apologize for her success. But she does occasionally marvel at it: "I never thought I'd have enough marbles in my head to do all this."