1. Kara's a bad ass super hero that isn't over-sexualized.
She busts through all of the female hero stereotypes by saving a plane from plummeting to its demise and joins forces with the government to help them stop alien criminals.
2. She a pretty normal person, despite the super-human strength and the flying.
Kara grew up on Earth, so she is awkwardly perfect. She's relatable makes you wish she was your actual best friend.
3. Winn.
He's the perfect sidekick and boy-next-door for Kara (and the rest of us). Not only is he not hard to look at, he is incredibly hilarious and brings a lot of comedic relief to the show - except for when you find out that his father a murderer, but it's chill. Even then, he's making you crack up. I'll take him.
4. It addresses issues like coming out.
Kara's adoptive sister, Alex, goes through the realization of her sexuality and opens up a great new facet of the show. Everything about the way that the show approaches the subject is great, from Alex's age to Alex's heartbreak.
5. Superman.
If you like looking at attractive journalists as much as I do, just watch the second season and bask in all he glory that is Clark Kent.
6. Cat Grant and all of her feminism.
As much as I love Winn, Cat is probably the best character in this show. She is unapologetically confident and takes no crap from anyone, yet she's incredibly honest. She is Kara's (and Supergirl's) biggest fan and secretly has a soft side. She built her company from the ground up and is a trailblazer. I've never been so inspired by a fictional character.
7. The immediate jokes and questioning of Kara's alias, Supergirl.
From episode one, the writers addressed Kara's superhero name. The irony and lightness of the subject is exactly what reeled me in and kept my attention. The beauty of the show is laughing at the slightly sexism of it all - which is automatically forgotten when Kara punches her first bad guy.
8. All of the "save the planet" talk.
Climate change is a huge topic in today's world, and climate change was a major factor in the death of Kara's home planet, Krypton. No wonder there's a lot of talking about how to save Earth. It's pretty interesting and the best way to promote saving our planet. If the aliens know what could happen and agree with it, so should humans!
9. Mon-El and the revealed discrimination between species.
When Mon-el arrived, I expected a new love interest for Kara, and I wasn't that excited about it. However, it was revealed that Mon-El is from a neighboring and rival planet to Krypton - Daxam. Kara grew up learning about people like him, many of those "facts" being rude, hateful stereotypes, and Mon-El was raised the same way when it came to learning about Kryptonians. Their relationship is the perfect example for the disputes and misunderstandings of today.
10. The significance of "aliens" and the citizenship and rights issue.
A good bit of the problems and bad guys that Supergirl has to face are because of the government working on making citizenship and rights available for aliens from other planets and how they are treated in general. Wow, it seems vaguely similar to problems with immigrants' rights seen today.
11. James.
Clark Kent's best friend makes his way into Kara's work life and quickly is told about her Supergirl secret. He's the coolest, sweetest, most handsome photojournalist a girl can get, and Kara struggles between their friendship or making it something more. Whatever happens between them, James Olsen is here to stay (in my heart forever).
12. Most importantly: the Danvers sisters' relationship.
Alex and Kara make the show. Not as separate characters but as sisters. Their relationship is strong and handles everything that is thrown at it. Neither one of them could make it without the other, and that's the beauty of Supergirl.