By now, Ween fans will have heard how the band surprised Les Schwab Amphitheater on Saturday by playing its sixth album “The Mollusk” in its entirety to kick off its sprawling, 2½-hour set.

The move, when announced by frontman Aaron Freeman (AKA Gene Ween) from the stage shortly after 7:30 p.m., truly did surprise. The band didn’t advertise or tease “The Mollusk” before the show, and a quick look at the band’s set lists at setlist.fm shows it didn’t do it again at previous or subsequent shows.

The performance itself, which marked the album’s 20th anniversary, was also surprising, with the band digging into a number of songs it hadn’t played in years (“It’s Gonna Be (Alright)” and “Cold Blows the Wind,” two of the album’s most touching songs — and stone-cold highlights of this show).

But the actual decision to play “The Mollusk” — over, say, 1994’s breakthrough “Chocolate and Cheese” or 1990’s “GodWeenSatan: The Oneness” (which actually did get the live, full-album treatment in 2001) — isn’t too surprising at all, 20th anniversary or not. The band’s sixth album, released in 1997, marked the final formation of the quintet that still tours as Ween to this day: original architects Freeman and Mickey Melchiondo Jr. (Dean Ween), bassist Dave Dreiwitz, keyboardist Glenn McClelland and drummer Claude Coleman Jr.

It’s also arguably the most “Ween” album there is, touching on everything that makes this cult band a favorite of jam-heads, punks and other misfits alike. At various points throughout the 14 tracks, Gene and Dean deliver sludgy rock epics (“Ocean Man”), demented sea shanties (“The Blarney Stone”), raging hardcore (“I’ll Be Your Johnny on the Spot”) and of course, a hefty dose of their demented humor (not sure I can print the song title we’re probably all thinking of now).

It made for riveting listening and viewing (at least, if the sun hadn’t been directly in the crowd’s eye-line for “The Mollusk” portion of the set). Dean’s guitar playing stole the spotlight in “Polka Dot Tail” and during a lengthy solo in the aforementioned “I’ll Be Your Johnny on the Spot”; his rant about bedbugs at the band’s hotel in Reno during “The Blarney Stone” was also pretty hilarious. Gene looked and sounded happy to be singing and playing with his old band again — at various points, he and Dean would face off with their guitars, grinning widely.

“The Mollusk” climaxed with the epic jam on “Ocean Man,” followed by “She Wanted to Leave (Reprise),” but Ween was far from done. The band played things fast and loose during the second half of the set, with a speed-demon version of “Take Me Away” setting the tone. Highlights included the sludgy “The Stallion, Part 1,” the bouncy yet dark “Roses Are Free” and the primarily instrumental “HIV Song.” An extended jam on “Buenas Tardes Amigo” gave everyone a chance in the spotlight (though with hindsight, Gene’s faux Mexican accent has not aged well as a joke).

The band played right up until the 10 p.m. curfew, leaving no time for an encore. Though Dean apologized profusely, it would be hard to believe anyone walked away from this one disappointed.

— Reporter: 541-617-7814, bmcelhiney@bendbulletin.com