In the midst of its blitz of 20th anniversary celebrations that include a Cameron Crowe-directed documentary, soundtrack and book, you might have expected Pearl Jam to hit NBC's "Late Night With Jimmy Fallon" with a classic like "Jeremy" or "Better Man" last night (Sept. 8). Instead, the Seattle band blazed in with a new, never-before-played song, "Olé," and frontman Eddie Vedder even got his, uh, mouth around a parody tune, "Balls In Your Mouth," duetting with host Jimmy Fallon. But that wasn't all, even before the episode aired, the band unexpectedly released the studio version of "Olé" for free on its PJ20.com site.

Download Pearl Jam's New Song "Olé"

Early in the show, as he reached for an acoustic guitar, Jimmy Fallon discussed a song he'd written about how he'd read that tarballs from the 2010 BP oil spill had been kicked up by hurricane Irene. The word "balls," a guitar, and a veteran rock band playing the show is an almost guaranteed recipe for comedy gold. And sure enough, halfway through, Fallon welcomed Pearl Jam singer Eddie Vedder to the stage so the pair could belt out the singsongy "Balls In Your Mouth" in tandem. Vedder sings the goofy "Balls in your mouth / Don't swim in the ocean you'll get balls in your mouth" in his instantly-familiar tenor looking around like "WTF am I singing?!" as the Roots sing back-up.

All kidding aside, Pearl Jam and director Crowe came to Fallon first to showcase the "Pearl Jam Twenty" documentary (airing an ultra-rare clip from the film of Vedder and Nirvana's Kurt Cobain slow-dancing at the 1992 MTV Video Music Awards), and the accompanying book. But the big surprise of the night was Pearl Jam debuting "Olé," a wailing rave-up, --- and releasing the studio version simultaneously for free at PJ20.com.

"Olé" is the second brand-new tune the band has debuted this week. Vedder told the crowd at the Sunday (Sept. 4) show of its PJ20 Festival at East Troy, Wis.'s Alpine Valley, reaching 20 years in Pearl Jam, "feels like a rebirth, a new beginning" before playing an untitled acoustic ballad written during the weekend, based around the line "so glad we made it."

Photos: Pearl Jam Caps PJ20 Fest With The Strokes, QOTSA, Chris Cornell All-Star Jam

Pearl Jam return to perform on tonight's episode of "Fallon," which airs on NBC at 12:35 a.m. ET. Crowe and the band will be in Toronto tomorrow for the premiere of the doc "Pearl Jam Twenty," which chronicle's its entire career, at the Toronto International Film Festival. Pearl Jam continues its Canadian tour on Sept. 11-12 in Toronto. The "Pearl Jam Twenty" book becomes available Sept. 13, the film is in theaters on Sept. 20 -- the same day the soundtrack is released -- before airing on PBS' American Masters series on Oct. 21 at 9 p.m. ET/PT.