Two-Headed Crowd.

Scenes From Saturday Night's Neutral Milk Hotel Show at The Majestic Theatre.

It was never going to be a normal night. There were just too many atypical variables in play.

A mercurial headliner with absurdly devoted fans. A venue — the gorgeous Majestic Theater — that doesn't normally host rock shows. Doors that opened a full 90 minutes before opening act Elf Power would take the stage.

Yes, chances we’re pretty high that something weird would happen.

And it didn't take long.

In the midst of “Lift the Shell,” Elf Power's second song, an interloper in a Philadelphia Phillies T-shirt appeared behind the band, watched as his friend removed the tarp from Neutral Milk Hotel's drum kit and then proceeded to thrash around on hose drums for a bit before being chased off the stage and out of the theater by a couple of roadies.

It was genuinely confusing. Was this part of the act — maybe an Elephant 6 inside joke?

As it turned out, it wasn't. It was just, as the crowd told Elf Power frontman Andrew Rieger when he asked them who the guy was, “some asshole.”

The incident was certainly disquieting, though. And it ensured the vibe was just a touch off for the rest of the Athens, Georgia-based indie quartet's otherwise enjoyable set.

The 40 or so minutes between Elf Power and Neutral Milk Hotel's sets ended up being welcome, too. Everybody had a chance to digest and laugh about what had gone down and to get into the right frame of mind for whatever was in store with Jeff Mangum and the musicians that helped him record NMH's beloved 1998 album In the Aeroplane Over the Sea.

That record, which Mangum says was inspired by his reading of Anne Frank's Diary of a Young Girl, would be front and center all night. The band played the entire thing — save for “Communist Daughter” — and much of the crowd was there with them the all the way, singing along with even the most surreal of Mangum's fever dream lyrics.

Mangum came on, solo, right at 10 p.m., briefly acknowledging the crowd before kicking into “Two-Headed Boy.” It was effective and visceral — to the point that, when the rest of the band came out for “The Fool,” the effect was something like a spell breaking.

Whatever intensity that might have been lost was more than made up for by the added texture the supporting cast provided. Julian Koster's musical saw work, Scott Spillane's multiple horns and Jeremy Barnes' drumming all combined with Mangum to fill out the atmosphere that's so essential to In the Aeroplane, giving touchstones like “The King of Carrot Flowers, Part One” and “Oh, Comely” the fleshing out they deserve.

The crowd was rapt. NMH's songs are so meaningful to the people they are meaningful to — the people who made sure this show sold out in less than a week when it went on sale last summer — that the headliners' set seemed, at times, like it was being revered more than enjoyed. That's not a knock on NMH; it was spectacular, but there were just times when the audience seemed a little tightly wound.

There was even a little heckling from those who apparently found the reverence a little off-putting. One especially vociferous gentleman kept shouting for Pantera songs. And with that came on some counter-heckling, which wasn't particularly helpful either. To his credit, Mangum handled the situation with aplomb. He shrugged off a shouted apology from the pit and appeared to be genuinely moved by the appreciative applause that greeted the end of each cut on the set list.

It wasn't a perfect audience experience, no, but by the end of the night most of the 1,700 or so in attendance seemed to have got what they needed: a cathartic, moving performance from an act that, as recently as two years ago, seemed unlikely to be heard from again.

And, for their part, Mangum and his band couldn't have been any better. They played 75 minutes of material, the newest of which is 15 years old, and their set came off as emotional and resonant as the music was back when it was recorded.

The show was something you were grateful you got to take part in — even if it made you more than a little sad that the band might never record anything new again.

The whole thing was special, really. Down to the idiot in the Cliff Lee shirt.