Darrell Brogdon, pictured here, is the host of Kansas Public Radio's Retro

Darrell Brogdon didn’t expect his hour-long, weekly celebration of “incredibly strange music” to remain on the airwaves when he started hosting Kansas Public Radio’s “Retro Cocktail Hour” in January 1996.

“I didn’t think it would last 20 minutes in the beginning because it was just so weird,” recalls Brogdon, whose programming grew out of a brief resurgence in what he describes as “Space Age bachelor pad” tunes in the mid-1990s. “It was such an odd thing for a public radio station to do — but on the other hand, I thought, if a public radio station doesn’t do it, who will?”

Turns out, Brogdon’s prediction was a little off. Twenty minutes? More like 20 years.

After two decades on air and 700-plus episodes, “Retro Cocktail Hour” is celebrating the milestone with a 20th anniversary concert 8 p.m. Saturday at Liberty Hall, 644 Massachusetts St.

The party begins Friday at the Jackpot Saloon, 943 Massachusetts St., with some “pre-celebration” jams courtesy of the local lounge-music outfit BongoTini at 7 p.m. Minneapolis-based Exotik-a-GoGo will take a break from their duties as house band at the very real Psycho Suzi’s Motor Lounge to headline Saturday’s event, which will also feature dancing, drinking (think classic “Mad Men”-style drinks with a little “island flavor,” Brogdon says), a photo booth and plenty of “Retro Cocktail Hour” swag. Dressing up is encouraged but not required.

At 20, “Retro Cocktail Hour” is almost old enough to legally drink a martini, jokes Brogdon, seemingly in a nod to the Underground Martini Bunker where he records the show — which has since expanded from one hour to two — every week.

Culled solely from Brogdon’s vast (about 10,000 albums and CDs, by his count) personal music collection, “Retro Cocktail Hour” reaches far beyond KPR’s signal these days. It’s now broadcast on 20 public radio stations across the country, across the world at Radio New Zealand, and to an unquantifiable mass of listeners virtually everywhere else via live streaming and podcasts.

The show has even spurred a few copycats over the years, says Brogdon, but he doesn’t seem to mind. What’s exciting to him is the production of new music that pays homage to his favorite mid-century artists, and the fans — young and old — who love it along with him.

“It’s been an amazing experience. I hear from people all the time who tell me they just discovered this either by accidentally hearing the show on the radio or by stumbling across it on the Internet,” he says. “They had no idea this music exists, and they’re really turned on and captivated by it.”

KPR’s “Retro Cocktail Hour” airs Saturdays at 7 p.m. and Fridays at 10 p.m. Tickets for Saturday’s celebration range from $20 to $30, and can be purchased at the Liberty Hall box office or at www.ticketmaster.com.