Let's talk about Joan Watson.
When Elementary cast Lucy Liu to play Watson in its modern-day Sherlock Holmes adaptation, it could easily have been a case of stunt casting. (Just imagine a gender-bent Watson in the hands of Steven Moffat). Instead, Joan Watson has become one of my favorite characters on TV. Ever.
First, Joan Watson is not only an incredibly well-rounded character, but a "strong" one. I'm usually loathe to describe any character as a "strong female character," because of all the phrase's implications, but Joan is that rare adult female character that makes me want to be like her, without being something unattainable (having magic powers, nigh-impossible strength or skills with a sword, being badass but kind of evil along with it). As viewers, we can empathise with her, but she's also, I think, something of an excellent role model -- and those female characters can be few and far between (especially played by actresses in their forties. Lucy Liu is that rare actress that is older than the male actor she plays against).
Joan Watson is an empathetic, caring, often selfless character. She's dedicated to helping others, she's good at helping people, and she's always willing to listen. But she also won't take crap from anyone. She has boundaries, she stands up for herself, and she's firm and articulate in her own defence. When Sherlock says or does something unacceptable, she sure as hell is going to let him know. Sometimes she makes mistakes, sometimes she fails, and sometimes she's unsure of herself, but she is a very accomplished, very intelligent, and very engaging character.
She's also Asian American, and although I'm not the most qualified person to speak on this issue, it seems to me that her character and treatment in the show is what diverse representation should be like. Watson's gender comes up very occasionally -- off the top of my head, Sherlock makes a comment once that she immediately calls out as misogynistic, and she accuses another character once of being more concerned for her safety because she is a woman. Her race, meanwhile, is a complete non-issue. There are references to her heritage, such as one moment where she comments that she doesn't speak Mandarin "as well as her mother would like" and another where she gives Sherlock a Chinese herbal tea that her mother always used to make her when she was sick (a tea that Sherlocks dismisses as fake medicine, and which turns out to work). Watson's race is a part of her character and background, but it isn't a defining factor for us as the audience, or for any characters who interact with her. She isn't stereotyped or fetishized or any of the other things that often happen to the (very few) Asian American characters we see on TV. She's a fully developed character in her own right. And she also happens to be Asian American.
And then there's her relationship with Sherlock. When the existence of Joan Watson was first announced, critics protested that the writers were only making the character a woman so that they could have straight romance between the leads. Although it's been done before, I don't think there's anything wrong with having a romance between the two leads, if that's where the story goes. The idea that a female character is lesser because she's involved in a romantic plotline is absurd, as is the idea that having two male leads with unspoken, never-developed, potential romantic subtext is better representation than changing one of them into an Asian American woman. But that said, I think one of the strengths of Elementary is that the Sherlock/Watson relationship is not romantic. There's no will-they-won't-they tension here. Heck, as someone who's quite the shipper with other shows, I feel qualified to say that there isn't really any romantic tension there at all. Sherlock and Joan have an entirely platonic relationship. If there are any other shows built around the platonic relationship between a man and a woman (and a woman of color at that), I'm not aware of them. Sherlock and Joan's developing relationship is incredibly deep and complicated. They support each other, they advise each other, they piss each other off, and they are both mentors for one another in different ways.
And they are equal leads in the show. Neither one has more background depth than the other or more screen time for their current emotions and problems. Neither one is solely the teacher or the student. Joan is arguably the more emotionally stable of the two, someone who Sherlock really relies on, but this reliance doesn't mean she becomes absorbed into him and his story, as many such female characters are. She's not just someone for Sherlock to explain things to, or just someone who explains emotions to him when they go over his head. She solves mysteries and finds clues by herself. She holds him accountable for his behavior, and can both get understandably furious at him and offer him a sympathetic ear when he's ready to apologize. She and Sherlock have a partnership.
Also, I really like her fashion choices. And her earmuffs. And did I mention that she's a single woman in her thirties or forties who isn't particularly bothered by that fact, who is career focused but is sometimes unsure about herself or what she wants, and who is as accomplished and talented as hell? I want to analyze what a great character she is, and talk about how this is what female representation on TV should look like... but I also kind of just want be her best friend. Or just be her. And that, I think, is the key that makes her a truly fantastic female character. She is wonderful and realistic, but she's also badass and inspiring. And female viewers need those kind of characters just as much, if not more, than male ones do.