One aspect of Bishoujo Series, and the cause of many tropes such as The Unwanted Harem and Fundamentally Female Cast, is that you really shouldn't have too many important male characters. But, y'know, girls like girly things.
So instead, why not have a girl who likes the things that guys do? You may not want to use a crossdressing girl or even a Tomboy—just give her a Fan Boy personality. And if you're a male author, this is even better, because you can go for authenticity the reader immediately understands.
A lot of this depends on what the current stereotype of a fan is and finding a fandom that is noticeably gender-skewed (Moe Moe and Humongous Mecha are popular targets) but the cast will still have only one character who is a fan of something with an overwhelmingly male fandom, and especially for obscure older things the adult audience immediately recognizes.
Another bonus to this is that the character's "masculine" characteristics are technically arbitrary, and easily tweaked to specific situations. Fans are very willing to put up with a lot of old tropes they wouldn't normally tolerate if the character was actually male.
Anime and Manga
- In Ichigo Mashimaro, Nobue is jokingly described by fans as the Otaku Surrogate of manga author Barasui, due to her much mellower personality and tendency to hug little girls.
- Morinas in Simoun is a total Simoun otaku, who makes plastic models in her spare time is even planning to be male after going to the Spring.
- Konata in Lucky Star is a complete over-the-top Otaku, obsessed with anime and video games, mostly to allow for mentions of Haruhi Suzumiya, Galaxy Angel II, SHUFFLE!, Haruhi Suzumiya, Kanon, To Heart, Haruhi Suzumiya, and so forth... but very little of what most girls are expected to watch, save for a notable brush with Mari Mite (and a brief reference to Wedding Peach while the other girls talk about wedding dresses). This is lampshaded when Konata explains them as habits picked up to be closer to her father, although her friends then have more questions about her father's choice of habits...
- And she plays eroges. Y'know, the sort of videogame for men that features naked young girls. Is it a wonder that so many fans interpret her as a schoolgirl lesbian?
- Later made stronger by the introduction of two friends, one of whom is more of an 'Bukuro than Akiba' fangirl while another (relevant to the series) is a Yuri Fangirl.
- And later on in the manga, we get Izumi Wakase, a Closet Otaku who has Konata's sports and home economics skills (average), Kagami's studying skill (average), is a class representative (Kou Yosaka's also one) but not flat and has an older brother complex.
- Hikaru Amano of Martian Successor Nadesico: as big a Gekiganger fan as Akito.
- Haruka of Nogizaka Haruka no Himitsu—beautiful, popular, and... otaku (the eponymous secret)
- Kaede Mizuno from Nyan Koi loves anything yakuza related. A subversion on her part, since we're led to believe she's a Moe Moe girl.
- Yukari Tsukino from Ai Kora turns out to be a member of a doujinshi circle, and is also into cosplay and video games.
- Genshiken has several girls like this, the most prominent characters being a cosplay otaku and a yaoi fan. In the other hand, this IS a show about otaku, so it's justified.
- Kirino from Oreimo is a closet middle-schooler otaku and a popular fashion model. Kuroneko and Saori are these to—little wonder they met in an online community called "Otaku Girls Unite"?
- Noah Izumi from Patlabor is a borderline example. She loves Mecha—but in a very different way from most otaku. Polishing her Labor, naming it Alphonse, writing "This Labor is Mine" on its leg at one point...
- The title character of Ganota no Onna, Ganota Utsuski, is a beautiful business woman and a major Gundam otaku, with a particular obsession with Zeon and Char. There are a lot of other Gundam fans around and the manga has a lot of Gundam references, like her boss being Zabi Degwin.
- Then again, this is Char Aznable we're talking about.
- Most of the cast of Runaways. Nico likes books about monsters (a plot point at least twice), Molly has immense knowledge about the X-Men (even before she found out she was a mutant herself), Victor was programmed to worship and know almost everything about superheroes (except The Slingers). Gertie has the philosophical dorkiness of a Soapbox Sadie. Alex is a clear MMORPG fanatic. Other characters have their moments but they aren't as prominent.
Live Action TV
- Wendy Watson in The Middleman knows a great deal about sci-fi and comic books, especially years-old series with predominantly male fandoms.
- Mr. Simpson says, "Toby Isaacs, meet Kendra Mason, my biggest anime fanatics." Degrassi's biggest anime fanatics.
- 7th Heaven's Simon was going to get his first kiss from a pretty and experienced girl but when they were supposed to be kissing they started talking about comic books.
- Josephine "Jo" McCormick is one of the three typical average kids who love to read comic strips.
- Midori Komaki of Shin Megami Tensei: Devil Survivor is an otaku who spends the entire game dressed in cosplay (she is stuck in the costume due to the lock down, but she states doesn't mind), and often acts as a Magical Girl in a setting where society is breaking down and innocent people are being murdered by demons.
- Sanae of Touhou is eventually revealed to be a massive Humongous Mecha fan in Hisoutensoku. When she saw the eponymous giant figure, she immediately went after it, practically Squeeing at the opportunity to battle, or maybe even ride, the Humongous Mecha.
- Kimiko of Dresden Codak has been accused of fitting this trope by various critics, as an attractive female transhumanist and extreme technophile in a comic written by a man who has also written for various futurist publications. Your Mileage, of course, May Vary -- mad scientists, Otaku or otherwise, tend to be rather thin on the ground in real life.
- Kat from Gunnerkrigg Court. She's very interested in robots, The X-Files, videogames (particularly Metal Gear Solid), dance music (especially Orbital and Prodigy), and comicbooks (Batman and Hellboy). Occasionally, her interest approaches Fan Girl levels:
- A number of entertainers associated with the anime industry have "come out" as self-styled otaku. Probably the most famous example is Shoko Nakagawa. It is not clear whether these individuals are actually interested in otaku-ish pursuits, or simply consider it a smart career move to cash in on a ready-made fanbase. It almost certainly differs from individual to individual, and could well be a bit of both in many cases.
- Felicia Day. Star of Buffy and Dr. Horrible, among others, and creator of "The Guild", a web series about a bunch of MMORPG gamers. She even based her character's addiction to MMO gaming to her own self-diagnosed addiction to World of Warcraft.
- Chiaki Kuriyama, according to video interviews, has a house full of Evangelion stuff.
- Brittany Diamond of The Ship's Closet