There’s a particular kind of thrill that comes with watching a superhero television series slowly populate itself with characters you recognize from the comics. It’s the same feeling you get when you’re reading a novel and a character you weren’t expecting walks into the room. Smallville understood that feeling intimately, and over the course of ten seasons, it leaned into it more and more aggressively — sometimes brilliantly, sometimes awkwardly, but almost always with genuine affection for the source material.

The show launched in 2001 with a very specific promise, famously summarized by creators Alfred Gough and Miles Millar as “no tights, no flights.” The idea was to strip Superman down to his moral and emotional core and examine what made Clark Kent Clark Kent before he ever put on the cape. That’s a noble premise. What it meant in practice, though, was that Smallville had to find ways to tell Superman stories without actually telling Superman stories — and one of the most effective tools in the writers’ arsenal was introducing other DC Comics characters to fill the superhero-shaped hole in the narrative. Sometimes they used those characters as mirrors for Clark. Sometimes they used them as foils. And sometimes, honestly, it felt like they were just throwing familiar names at the screen and hoping the audience would be too excited to notice the seams. But the best of these appearances genuinely elevated the show, and a few of them rank among the most memorable moments in the entire series.

The Torch Was Passed

Let’s start with the most emotionally resonant DC cameo in the show’s run, because nothing else quite touches it. Christopher Reeve appeared twice on Smallville — first in the season two episode “Rosetta” and again in season three — as Dr. Virgil Swann, a scientist who had decoded the Kryptonian language and served as a kind of guardian of the truth about Clark’s origins. Reeve was, of course, the definitive cinematic Superman, and the weight of that legacy hung over every frame he appeared in.

What made the casting so ingenious was that Gough and Millar weren’t simply trading on nostalgia — though there was plenty of that to go around. Dr. Swann was written specifically to be the man who handed Clark the first real answers to the questions that had haunted him since childhood: Where am I from? What happened to my parents? Am I truly alone? Having Christopher Reeve be the one to deliver those answers wasn’t just fan service. It was a genuine passing of the torch, a narrative acknowledgment that this new Clark existed in a continuum that stretched back through decades of Superman mythology. The production flew their crew to New York to accommodate Reeve, who used a wheelchair and required additional assistance when traveling, and Reeve himself reportedly pushed for more dynamic staging between himself and Tom Welling, understanding intuitively that the scene needed to feel like an encounter between two forces rather than a simple information exchange.

Reeve died in 2004, before the show had finished half its run, and the show honored his absence by having Dr. Swann die off-screen in season four. It’s one of the quieter, sadder moments in Smallville‘s history — the departure of a character who had done more for the show’s credibility in two guest appearances than most recurring cast members managed in multiple seasons.

The Brain InterActive Construct

If Reeve’s appearance was about emotional legacy, James Marsters’ turn as Brainiac — introduced in season five as the Kryptonian artificial intelligence disguised as college professor Milton Fine — was about pure narrative electricity. Marsters, who Smallville fans of a certain stripe will also recognize as Spike from Buffy the Vampire Slayer, brought exactly the kind of coiled menace the role required. Gough and Millar were apparently so set on Marsters that they stated plainly: if he had declined, they would have replaced Brainiac with an entirely different DC villain rather than recast the role. That’s a remarkable level of confidence in a single actor’s suitability for a part.

What worked about this casting, beyond Marsters’ obvious charisma, was the specific flavor of danger he projected. Brainiac isn’t a villain who smashes things. He’s a villain who outthinks you, who is always three moves ahead, who wears a pleasant face while planning something catastrophic. Marsters described the character as focused purely on intent — “like watching a shark,” in his words — and that single-mindedness translated beautifully on screen. Marsters returned for four episodes in season seven before being finally dispatched, and the show was noticeably less interesting whenever he wasn’t around.

The honest critique here, though, is that Smallville never quite figured out how to permanently deal with Brainiac in a way that felt satisfying. He was “killed” and returned multiple times, and by the time the Legion of Super-Heroes exorcised him from Chloe’s body in season eight, the threat he represented had been diluted significantly by overuse. Smallville had a recurring problem with its villains — Lex Luthor notwithstanding — where it didn’t know when to let a threat land permanently. Brainiac was arguably the most egregious example.

Assembling the Justice League

Starting in season six, Smallville began doing something that felt genuinely ahead of its time: assembling a roster of DC heroes who would operate alongside Clark in a way that prefigured the cinematic shared universe model that Marvel would perfect years later. Justin Hartley’s Oliver Queen arrived first, initially as a romantic rival for Clark’s attention with Lois Lane and then as the show’s most consistent argument for what a functioning superhero looked like. Where Clark spent most of the series wrestling with whether to use his abilities, Oliver had already made his peace with vigilantism and was more than willing to call Clark out on his paralysis. The dynamic between the two was one of the more intellectually engaging threads the later seasons offered.

Around Oliver, the show gradually assembled a loose Justice League that included Alan Ritchson as Arthur Curry (Aquaman), Lee Thompson Young as Victor Stone (Cyborg), and Kyle Gallner as Bart Allen (Impulse). The episode “Justice” in season six, which brought these characters together for a team mission, was a genuine event — the kind of moment where Smallville fully committed to the larger DC universe it had been cautiously dipping its toes into. The costumes were minimal, the budget was clearly strained, but the idea of it landed with real force.

The honest critique, again, is one of underutilization. Aquaman, Cyborg, and Impulse were all fascinating characters who appeared briefly, made strong impressions, and then largely vanished from the narrative. Smallville introduced them with enough care to make you want more and then kept pulling the rug out. Part of this was budgetary — maintaining a roster of recurring heroes is expensive — and part of it was the show’s fundamental commitment to Clark’s singular perspective. But it left the Justice League feeling like a series of promising pilots for shows that never got made rather than a coherent superhero ensemble.

The Villains Gallery

Smallville‘s approach to its DC villains was similarly mixed. Callum Blue’s Zod, introduced properly as the season nine antagonist, brought genuine menace to what had previously been a somewhat abstract threat. The decision to make him “Major Zod” rather than the general audiences knew from the films was a smart one — it allowed the character room to develop rather than simply imitating Terence Stamp’s iconic performance. Blue played him with a wounded arrogance that made him more compelling than a straightforward conqueror would have been.

On the other end of the spectrum, Doomsday — reimagined as Davis Bloome, a paramedic played by Sam Witwer — was one of the show’s more ambitious swings. Taking the character who famously killed Superman in the comics and recasting him as a tragic, essentially good man who transforms against his will into something monstrous is genuinely interesting on paper. Sam Witwer gave the role more emotional depth than it probably deserved given the constraints of network television, and the tragedy of his story — culminating in his death at Jimmy Olsen’s hands — landed harder than most of season eight’s plotting warranted. The criticism here is that separating Doomsday from Davis using black kryptonite and then dispatching the monster off-screen was the kind of anticlimactic resolution that Smallville occasionally resorted to when it had written itself into a corner.

Phil Morris as John Jones — the Martian Manhunter — deserves special mention as one of the most consistently well-handled recurring DC characters in the show’s run. Morris played the character with a quiet authority that felt exactly right, and the show used him sparingly enough that his appearances retained their weight. He also appeared in season ten’s “Absolute Justice” alongside Hawkman (Michael Shanks) and Stargirl (Britt Irvin), an episode that represented Smallville at its most ambitious and, largely, at its most successful in translating DC mythology to live action.

What Smallville Got Right

The broader achievement of Smallville‘s DC character work was that it existed at all and, in the best cases, did more than simply wave at recognizable names. At its peak, the show used characters like Oliver Queen and Virgil Swann as genuine narrative tools — as ways to challenge Clark, deepen the mythology, and make the argument that the Superman story was bigger than any single character. The casting was frequently inspired, the writing occasionally matched it, and the ambition was almost always genuine even when the execution fell short.

Looking back at it now, Smallville was doing something that the industry has since recognized as enormously valuable: building a shared superhero world on television with enough care for the source material to satisfy longtime fans and enough accessibility to bring in new ones. It did this years before anyone fully understood that was what it was doing. The “no tights, no flights” rule that originally defined the show’s identity eventually became its biggest limitation, and the gradual relaxation of that rule — as more heroes and villains arrived in increasingly recognizable forms — was arguably the best thing that happened to the series in its latter half.

The cameos and guest appearances weren’t just crowd-pleasing additions. They were, in many ways, the show’s most persuasive argument that Clark Kent’s story had always been bigger than Smallville, Kansas. The heroes and villains who passed through that town on their way to somewhere else were proof of it.