In Superman & Lois episode "All Is Lost," which aired on June 7, 2022, Jordan decides to keep his secret identity from Sarah so she can be safe. This is a common trope and a heartbreaking decision that many members of the Kryptonian family make as they believe that their supernatural abilities could place the ones they care about in harm's way.
Kara Danvers, from Supergirl, also dealt with these issues - until she decides to reveal her human identity to the entire world in the finale. However, before that, she had to constantly lie so people wouldn't find out about her superhero persona. Funny enough, Kara is a terrible liar, and it's miracle no one - besides Cat Grant - figured out who she really was.
Kara "Accidentally" Finding A Hidden Save
In season 4, Alex has to erase Kara's superhero persona from her mind so it won't affect her work at the D.E.O. However, Kara is not very good at keeping her secret identity from her sister. When Kara and Alex find each other at a murder scene, Kara tries to subtlely help the case without her sister finding out about her powers.
It's safe to say Kara didn't do a great job. The first thing she does is slightly take off her glasses while squinting to be able to use her x-ray vision. If Alex had looked her way, it would have been entirely too suspicious. She also pretends to accidentally find a hidden safe, while leaning unnaturally against it. They are all rookie mistakes, but given that Alex had known about Kara's extraterrestrial persona since they were children, it's probably out of sheer awkwardness that she behaves this way.
Kara Telling Cat Grant She's From This Planet
Everyone is familiar with Cat Grant's sassy comments. In fact, it is her wit that makes Cat one of the most liked characters in the TV show. So when she sarcastically asks Kara from which planet is she from, no one is really surprised. What's hilarious is Kara answering "umm... From this one," while nervously fidgeting with her glasses.
What makes this lie particularly ridiculous is that she didn't even have to answer the question, as it was a rhetorical one. With Kara losing her cool even in quotidian moments, it's not a surprise Cat Grant was eventually able to figure out her superhero persona.
Supergirl Telling Lena She Was Having Coffee With Kara Danvers
In season 2, Kara and Lena are on the phone when Lena is suddenly attacked by two men at L-Corp. When Kara realizes that Lena is in danger she immediately goes to her office, arriving just in time to catch Lena as she's falling from her balcony. Lena asks her how she managed to get there so quickly, and Supergirl replies, stuttering, that she was having coffee with Kara Danvers at that very moment.
What's even funnier is that Lena replies "How lucky!" and she doesn't even suspect that the girl of steel is lying through her teeth. Even if Lena could believe such a coincidence, the fact that Supergirl took a second to reply and was clearly stuttering should have been enough to put everything together.
Kara Pretending To Pass Out In Lena's Plane
This is one of Supergirl's most iconic scenes, mostly because it's a classic Super moment (Clark Kent even has an almost identical scene). When Lena's plane starts failing due to being under attack, Kara sneaks out to safely land the plane and comes back just in time to pretend she passed out in one of the passenger's seats.
This scene is hilarious because Kara even makes the effort to put her glasses askew to make the scene more believable. Lena even has to shake her a bit to wake her up. The whole thing is histrionic, and probably the only reason Lena doesn't suspect a thing is because she's still scared about what just happened.
Kara Telling Cat Grant's Son That She's Also From This Planet
When Cat Grant entrusts Kara to take care of her son, Carter, she has to pick him up from school. Carter is a timid boy who can barely look people in the eyes, so Kara tries to break the ice by telling him how much she used to love school when she was his age. She also tells him that she loved learning everything "about this new planet." As if that is not suspicious enough, she tries to cover her mistake by adding "that I'm also from."
In the first seasons, Kara has a hard time hiding her Kryptonian identity. Maybe it's because she's still young or she's not used to interacting often with people who don't know her secret. Whatever the reason, these kinds of comments slip out in casual conversations and people usually don't know how to react.
Kara Pretending To Be Exhausted In A Spinning Class
In the middle of a spinning class with Lena, Kara is comfortably riding her bike without even breaking a sweat. When Lena makes a comment about the workout, Kara finally realizes this is not common human behavior - at least not for someone who's not supposedly in shape, like Kara Danvers. She then pretends to be exhausted and comments on how she "can feel the burn."
This is one of the funniest moments in Lena and Kara's friendship. Kara is probably not used to feeling tired or having any sort of challenges. On top of that, she probably doesn't do any common exercises, such as spinning, because she doesn't need to try to be in shape. So, it makes sense that she forgets how humans usually react to this sort of extenuating activity.
Kara Flying With Lena Without Even Changing Her Clothes
After Lena is poisoned, Kara doesn't even hesitate in taking Lena to the D.E.O. as soon as possible. This means Kara flies around in her cardigan and glasses with Lena in her arms. When Lena wakes up, she tells Kara that she had a dream where she was carrying her, to which Kara replies "I was? Like Supergirl? I wish!"
Even though Kara had to act immediately to save Lena's life, she totally risked her identity by not changing her clothes. Even if Lena thought the whole thing was a dream, someone else could have seen her. On top of that, her reply to Lena's comment is definitely suspicious.
Kara "Sneakily" Using Her Powers
When Mercy Graves attacks L-Corp while Kara is in Lena's office, the superhero has a hard time getting away to change into her Super suit. Lena keeps insisting that Kara should be by her side to keep her safe, and Kara has to constantly find ways to avoid attacks without Lena or Eve noticing she has super powers.
Even though this scene is hilarious, it is also probably one of the reasons why Kara should have decided to tell Lena sooner about Supergirl. Kara manages to eventually change into Supergirl and no harm is done, but it's unbelievable that no one around actually saw her while she used her powers.
Kara Forgetting She Can't Get Her Nails Done
In an Arrowverse crossover, Kara goes out with Felicity Smoke, Iris West, and Caitlin Snow to get their nails done because of Iris and Barry's wedding. When the manicurist tries to file Kara's nails something terrible happens: the machine actually starts burning up. Kara tries to cover up the accident by telling the woman that she takes a lot of keratin.
In this very funny scene, Kara forgets she's not human and lets the manicurist try to do her nails, even though they're indestructible. Maybe it was because she's thinking about Mon-El, who just came back to Earth - married, or because she's not usually in this sort of situation, but whatever the reason, the excuse she gives the manicurist is nowhere near close to being believable.
Kara Telling Lena, She Flew There... On A Bus
When Kara and Lena barely know each other, Kara visits Lena in her office to interview her. Lena, ever so polite, offers to validate her parking ticket, but Kara tells her that's not necessary because she flew there. Immediately realizing her mistake, she adds that it was on a bus. Fortunately for her, Lena doesn't even question her and they go ahead and start the interview.
Even though Lena miraculously didn't react to Kara's comment, this is possibly one of Kara's worst attempts to conceal her superpowers. Lena is obviously aware of Supergirl and other types of beings with extraordinary abilities, so it's really lucky that Lena didn't suspect a thing.