Usually, when thousands of eager fans pile into an arena for a concert, there's an expectation: Maybe it's a performance on an international tour that finally reached Dallas. Maybe the original band members are back together, finally burying their hatchets for another go-round. Or maybe it's just another stop of a summer tour where rockers spread some joy and cash some checks.

But what are we to make of Smashing Pumpkins' comeback tour that isn't really a comeback? What about a concert that has a few familiar faces on stage — but not everyone from the group's glory days? When does a modern rock band finally fade into the classic rock realm, and consequently, what does that say about the fans still hanging on?

These were certainly questions on the minds of attendees at Wednesday night's Smashing Pumpkins concert at American Airlines Center.

But there was another, arguably more important question: Is this whole thing just a gimmick?

The questions about the band's Shiny and Oh So Bright Tour began to swirl as soon as leader Billy Corgan, one of the unquestioned icons of the '90s alternative rock era, announced that he and original band drummer Jimmy Chamberlin would be joined on tour by James Iha, the band's estranged, original guitarist who hadn't been with the Pumpkins for 18 years.

The query posed most often was regarding the status of original band bassist D'arcy Wretzky. As the band announced its plans for the two-month summer tour, news reports tended to focus more on the feud between Wretzky and Corgan (one that would keep her off of the tour) than on the tour itself.

Add to that the fact that Chamberlin has been touring with Corgan steadily for the past few years, and this "classic lineup" collection felt more like a "hey, we're friends with James Iha again" shindig.

And if that's what this was, then it was a stellar one. The Dallas concert was a three-hour marathon, packed with the band's biggest hits, deepest cuts and a few inventive covers that were so enjoyable that any of those pesky questions were quieted.

Consisting of songs almost entirely from the group's first five albums, dating from 1991 to 2000, this was a concert designed to celebrate a legacy. Cynically, this tour's focus on the older, more popular material could also have been easily construed as a ploy to lure suspicious fans into venues much larger than the Pumpkins had recently played. (For local examples, the Pumpkins have played Verizon Theatre in Grand Prairie and Majestic Theatre in Dallas over the years.)

But again, if that was indeed the case, well, it worked. Although the 300 level at the top of the arena was curtained off, the rest of the available seating was crowded enough. And that crowd made its roaring, passionate voice heard when Corgan walked on stage by himself, carrying only an acoustic guitar to perform "Disarm," from 1993's Siamese Dream, a tune many consider to be a top five song from that entire decade.

Lead singer and guitar player Billy Corgan performs with the Smashing Pumpkins on July 18, 2018 at American Airlines Center in Dallas. (Ashley Landis / Staff Photographer)

Once the band joined its enigmatic leader on stage, the night really clicked. Going from "Siva" to "Rocket" to "Rhinoceros" and to "Drown" offered an urgent showcase of the group's first years. In the decade's worth of songs we heard throughout the night, we got to also hear the styles that go into the Pumpkins' sound.

Elements of hair metal, dream-pop, electronic, grunge, punk, pop and folk pervade the band's catalog in one point or another. The Smashing Pumpkins are all of those things, yet none of them at the same time, because few of their individual songs stay within any of those templates.

Given Corgan's unpredictable, oft-unexplainable public persona, it was refreshing to not only hear his voice in fine command, but to see him in good spirits. Few rock vocalists have the palette of tones to work from as he does. Whether he was sending his alien caterwaul out in "Zero" or "Cherub Rock," utilizing his low-register power-whisper in "Thirty-Three" or "Landslide" — or both, as he capably did in "Stand Inside Your Love," "Mayonnaise" and "Ava Adore" — Corgan embraced his role as ring-leader with deft, dramatic flair.

PHOTOS: The Smashing Pumpkins concert in Dallas

That flair included a few costume changes for Corgan, complete with ornately stitched floor length coats and flowing gowns. And covers of David Bowie's "Space Oddity" and Led Zeppelin's guitar store staple "Stairway to Heaven," both of which could've been cartoonish, were unique enough to not look away. Corgan let out an unexpected chuckle in the beginning of the otherwise ominous "Eye," and flubbed a line in "Stand Inside Your Love." Both miscues were endearing in the live setting.

The Smashing Pumpkins' pseudo comeback tour included a few costume changes by lead singer Billy Corgan. (Ashley Landis / Staff Photographer)

The tempo-killing, somber piano-intensive "For Martha" and "To Shelia" could've been left off the set list, but then, it wouldn't have been a proper Pumpkins show without an earth-flattening dose of mood and longing. Tempo wasn't an issue at the end, as the adrenaline-activating "Today," "Bullet with Butterfly Wings" and "Muzzle" propelled the night into a triumphant close.

These are songs and albums that simply can't be excluded in any serious discussion of '90s rock music or the Clinton-era alternative boom. And so, again, was this concert just one big nostalgia-trip gimmick? Perhaps.

The most important question, however, provides the only answer that really matters: Did this gimmick work? Absolutely.