Lana Lang should have figured out Clark was an alien without him ever having to tell her in Smallville. After years of keeping her in the dark, Clark finally told Lana the truth about his alien origins in the season 6 finale. She had never come close to guessing this secret, but one detail suggests she should have known before that moment.
Lana had good reasons for believing that Smallville's Clark was hiding a huge secret from her, but the show consistently found ways to keep her from knowing exactly what it was. It wasn’t until season 6 that this aspect of their relationship began to change. In “Promise,” the episode where Lana married Lex Luthor, Lana set a trap for Clark so that she could find out once and for all if he really had powers. Her deception confirmed her suspicions, but she remained oblivious to the fact that Clark was an alien. Until the season 6 finale, she assumed that Clark - like so many others in Smallville - received his abilities from the Kryptonite that fell during the meteor shower.
Smallville Season 5 Proves Lana Should Have Figured Out Clark’s Secret
Events in season 5 reveal why Lana should have realized that Clark had to be an alien, rather than just one of the meteor-infected Smallville residents. At the beginning of season 5 when the three Kryptonians emerged from their spaceship, Lana witnessed them using their powers and also saw Lex use them when he was possessed by Zod at the end of the season. Because of this, she knew firsthand that Kryptonians were capable of superhuman strength, speed, and heat-ray vision. What’s important about that is that all three of these abilities were demonstrated by Clark when she was spying on him and Chloe in “Promise.”
The specific powers used by Clark in the episode were a massive clue to his true identity, yet the comparison was somehow lost on Lana. They have a clear link to season 5’s Kryptonians, but Lana never did connect the dots between Clark and the aliens. Making Lana not figuring it out even worse was the scene in “Promise” where John Glover's Lionel Luthor dropped a hint about Clark having a weakness. She knew from her experience with the three Kryptonians that members of their species also have a weakness (Kryptonite.) This was just one more reason why it would have made sense if Lana at least considered the possibility that Clark was from another planet.
Why Lana Never Guessed That Clark Was An Alien
Perhaps the only explanation for Lana not reaching what should have been an obvious conclusion relates to her love for Clark. In Smallville season 5, Lana referred to the Kryptonians as “things,” making it abundantly clear that she didn’t acknowledge them as actual people. She didn’t see any humanity in them, which may have to do with why it never once occurred to her that someone she loved and had known her whole life could secretly be a Kryptonian.