Ten years ago, I'm sure I proclaimed that Tenacious D was, by far, the greatest musical comedy duo ever showcased on HBO. And had you bet me that a better two-man group would surface on cable TV, I would've gladly taken that wager.

I'm surprised to be writing this, but a better, more clever and even funnier group than "The D" exists. It's New Zealand's Flight of the Conchords, and a sold out Riverside Theater soaked in their brilliant two-hour show Sunday night. The talented pair, whose eponymous series finished its rookie season on HBO in September, turned two guitars and a couple of old-school MIDI instruments into the kind of concert that sticks in the head for days.

Quite simply, FOTC mixed funky jams, clever lyrics, deadpan shtick and witty improv comedy into a masterpiece show. If you've never heard them, think Bee Gees meets Tenacious D meets David Bowie meets the Pet Shop Boys. They're just that talented, just that playfully soulful -- and just that hilarious.

Jemaine Clement and Bret McKenzie ran through most of the favorites from the first season of their show, opening with "Robots." They reacted surprisingly well to a borderline annoying crowd, clearly happy to be there, but boisteriously heckling beyond the point of being amusing.

But that didn't stop the guys, who parlayed the random, lame shouts into their conversational banter that, at times, stretched too long -- but always stayed witty. While totally deadpan on HBO, they allowed themselves to smile, especially when their impromptu reactions to the audience legitimately made each other laugh.

They played "I'm Not Crying," "Business Time," "Hip-Hopopotamus vs. The Rhymenoceros," "Mutha Uckas," "Albi the Racist Dragon" and much, much more, including some great new tunes -- usually dealing with the omnipresent subjects of breakups and ex-girlfriends.

They ended the show with "Bowie," a spaced-out time travel conversation between two David Bowies (it translated a little better on the show).

Clement and McKenzie came back for two encores, wrapping with the Pet Shop Boys inspired, "Inner City Pressure."

Arj Barker, who plays the stoner character Dave on the HBO series, opened for the band. His observational style of humor nicely warmed up the crowd, and while pretty unpolished, he was legitimately funny.

All told, both Flight of the Conchords and Barker worked hard and left the crowd happy on this Sunday night show.

Considering their HBO series, which fortunately will air another season, is all about the FOTC striving to get noticed, it's wonderfully ironic to see a packed house singing along. I haven't seen such excitement in a musical comedy act since Tenacious D. And while I never thought I'd see it again, Flight of the Conchords delivered -- song after song after song.