For any series not aimed solely at females, odds are high that only one female will be in the regular cast.
The Smurfette Principle is the tendency for works of fiction to have exactly one female amongst an ensemble of male characters, in spite of the fact that roughly half of the human race is female. Unless a show is purposefully aimed at a female viewing audience, the main characters will tend to be disproportionately male. Said only woman will almost always be used as half of a romance subplot.
In many series, men will have various different personalities, but women will always be The Chick. Thus, by The Law of Conservation of Detail, you only need one.
In other cases, the women are feminized versions of existing male characters.
This trope has lessened over time, but even now it often applies to animated fare aimed at boys or a general audience. This is especially serious when the regular cast is full of synthetic entities or other species which have a voice or are sufficiently humanoid; these will always be more masculine than feminine, with any feminine examples receiving special attention, suggesting that women are merely an unusual subtype of men.
Why does this trope happen? Often, the problem lies with the source material — the work's an adaptation of something written or created decades before equal recognition for women started to gain momentum. Sometimes, however, writers will try to correct this problem by inserting a few more female characters or at least an Affirmative Action Girl.
When the time for merchandising comes, unless the cast is all female, manufacturers won't create as many (or sometimes not at all) figures of the female members as they would males of the franchise even if the series is Merchandise-Driven (or at least, until the mid-90s). This creates a vicious cycle in which The Smurfette Principle is upheld by both toy manufacturers and TV writers, each reasoning that the other will enforce it anyway. This may be because, statistically, companies believe that action figures of female characters don't sell as well as the male ones, all evidence to the contrary. Of course, the shortage of female action figures to base those figures on can lead to another vicious cycle.
In classic comedy animation or shows, especially slapstick, women are often absent because hitting a girl just isn't consideredfunny. (In the case of harmless Amusing Injuries, this isn't always the case.)
This trope can also be justified by its accuracy in certain contexts. It is fairly realistic for armies, police forces, adventuring parties, and similar groups to be predominantly male, especially if set in a non-Politically Correct History.
As noted in the examples below, this trope is nearly universal in all forms of media. Most writers try to balance this out with Positive Discrimination, making the girl more intelligent and level-headed than everyone else, but it still doesn't change the simple fact that there's only one of her. Usually, all it does is turn her into a Mary Sue for everyone to loathe.
Writers who recognize the problem after a season or two may expand the cast with Affirmative Action Girls. This is usually more effective.
Interestingly, this can extend to Mooks and the Monster of the Week with Monogender Monsters, to avoid the Unfortunate Implications of violence against women.
Action Girls and other strong, usually supporting female characters who are the only girl or are only one of a few girls in the group are sometimes called "minority feisty" or "token feisty." They may even have some commentary about sexism or male domination, but the majority of the characters are male.
The name of this trope was first coined by an article in the New York Times printed April 7, 1991, called "The Smurfette Principle". The article discussed the negative message which this trope gave its young audience: that males are individuals who have adventures, while females are a type of deviation who exist only in relation to males.
Contrast Two Girls to a Team, The Bechdel Test, Girl-Show Ghetto. This is also Distaff Counterpart to The One Guy. See also Smurfette Breakout when the character becomes popular on her own, and Territorial Smurfette when another female is added to the show and the character reacts negatively.
Played straight in the Empath: The Luckiest Smurf story series, since it's mostly based on the cartoon show, though the reason for the disproportionate number of male Smurf characters is that Papa Smurf's generation (which consisted of both male and female Smurfs) ended up having mostly male offspring, with only one female Smurf offspring, which turned out to be Sassette.
Up to Eleven in My Little Unicorn. According to Word of God, the population of Unicornicopia consists mostly of males. While the story has at least five female winged unicorns in it, only Starla (who is mostly there as the Love Interest) and Dementia have any form of slight significance to the overall plot.
Like its source material, the 2011 film The Adventures of Tintin exemplifies this trope. It has only a handful of female characters, and only two of them (Tintin's landlady Mrs. Finch and opera singer Bianca Castafiore) have names, dialogue, or any importance to the plot.
Megamind has a single Brainbot with a pink frill and lipstick. The DVD commentary states that she was an Invoked Trope, and considered "the Smurfette of the Brainbots". There is also Roxanne Ritchie.
Susan/Ginormica is the only woman in the main cast of Monsters vs. Aliens ("We are in the presence of the rare female monster."). However, she is the main character and has the most Character Development of anyone else, going from The Chick to Action Girl. The rest of the female characters are in small, stereotypical roles, with the exception of the girl making out in a car, which reverses the usual role by being more assertive than her milquetoast boyfriend.
The jury is still out on whether Insectosaurus is female or not, since he/she has eyelashes in his/her final form as a butterfly. Even so, the ratio of female monsters to male would still be 2:5.
7 is the only female ragdoll in 9. The twins 3 and 4 never talk, so their gender is ambiguous, but that's still a 1/2/6 ratio. On the other hand, only 7 is a fighter or independent by nature. Justified; they all seem to stem from the Scientist's soul, so odds of his soul containing a lot of feminine qualities are very low.
Might be justified even without that. It's considered a pretty solid theory that everybody (or at least almost everybody), has psychological qualities of the opposite gender, to a greater or lesser extent depending on the individual.
The Disney Renaissance films were a bit bad about this, though some were improvements:
The Little Mermaid - Ariel as the protagonist and Ursula as the villain. All of the supporting cast are male, making it a 6:2 ratio. Ariel's sisters have no importance and Carlotta the maid has only a handful of lines. The sequel adds Ariel's daughter Melody, has another female villain and bumps up Carlotta's importance somewhat.
Aladdin has only Jasmine. Aladdin's mother was originally in the film too but got cut. The protagonist (Aladdin), main villain (Jafar), best friend/mentor (Genie), and sidekicks (Abu and Carpet) are all male. The Sultan rounds out the cast of male characters. Female characters do populate the world so this is arguably faithfully reflecting the kind of world where power games are played out between men and Jasmine's story would revolve around the necessity of her finding a man to marry. It still doesn't solve the diversity/representation issue but it's somewhat logical.
The Lion King - Nala and Sarabi are the only female protagonists. Nala is there as the Token Romance while Sarabi is Simba's mother. Somewhat balanced out by having Shenzi as a prominent villainess. Again, the sequel fixes this by making the protagonist Simba's daughter, the villain being the female Zira and also including her daughter Vitani. But again Sarabi and Shenzi were dropped and Nala was even less important.
The Hunchback of Notre Dame - only Esmerelda, making the main cast at a 3:1 ratio. Likewise in the gargoyles, it's 2:1 with Laverne as the only female.
Mulan - Mulan herself is the only woman with any importance. Her mother and grandmother feature prominently at the start. In this case it's probably justified since there aren't supposed to be any women in the Chinese army.
Other Renaissance films were much better:
Beauty and the Beast - Belle is the protagonist with Mrs Potts in a big supporting role. There's also a sizeable collection of female side characters like the wardrobe, the feather duster and Gaston's three Bimbettes.
Tarzan - Jane is Tarzan's prominent love interest. His mother Kala plays a big role in the story and his best friend Terk is also female (though voiced by Rosie O'Donnell leading to some Viewer Gender Confusion). Word of God confirms that Sabor the leopard is female too.
Two recent Disney films, The Princess and the Frog and Tangled, are ostensibly aimed at girls, and have female lead characters, but otherwise they both have 1:3 female-to-male ratio — female lead, male love interest and co-lead, two male (animal) supporting characters. Then one woman in a supporting role (a mentor in Princess, a villain in Tangled). Princess does slightly better, featuring Tiana's mother and her supportive friend, Charlotte.
Frozen only has two female characters, but the bonus is that they are both the protagonists. Aside from Anna and Elsa, the only other females in the film are in the trolls (who are one-scene characters) and the girls' mother who dies within the first twenty minutes. The core "team" thus consists of Anna, Kristoff, Sven, and Olaf giving us a 1:3 ratio. Adding in Hans and Elsa the ratio of important characters goes to 2:4.
For all their perfection, one major complaint about Pixar is the lack of films that have a notable number of prominent female characters:
Toy Story's main cast includes a young boy's toy collection, with predictably male-oriented rather than girls' toys. Bo Peep was the only female in the cast, a domestic woman and Satellite Love Interest with no part in the main action. Toy Story 2 and 3 even out the gender inequality, though not by much. Even though Toy Story 3 had many more female characters than the other two, it should be worth mentioning that Andy got rid of Bo Peep.
A Bug's Life, despite having a few female royalties, is guilty of the Insect Gender Bender; biology dictates its protagonist should have been female. The Seven Samurai-esque troupe has a 3:1 (6:2) male-to-female ratio.
The only major female characters in Monsters, Inc. are a little girl with limited dialogue, the forgettable love interest Celia, and Roz the undercover CDA agent, who has little screen time. The ratio is 4:2.
Finding Nemo has 9:3. The writer explains on the DVD commentary that in fact Dory was originally male until he saw Ellen DeGeneres on television and realised that was the sweet-but-scatty tone he was looking for.
The Incredibles averts this by being demographically balanced (main cast: two female, two male; supporting cast: one each; villains: one each). Also, each of the adult females are shown to be independently competent, and the main villain finds out that treating his female ally like an expendable resource will have consequences.
Cars: the ratio is 9:3. In the first film, the racecar sponsoring RevNGo is actually the only female competing in the Piston Cup, and in the sequel, Carla Veloso, the Brazilian racecar is the only female competing in the World Grand Prix.
There is only one female rat in Ratatouille, who speaks to Remy at the end of the film. She only gets one line, though. Remy's family consists of a father and a brother. The major human female character, Colette, is very much aware that she is the only female chef in the restaurant and in a definite minority in the profession in general. She was forced to claw her way up and as a result, feels that she has to be tough and defensive to succeed in a career she worked so hard for. However, when her protégé, Linguini (and secretly Remy the Rat as well), make it clear that they deeply respect her expertise, she softens to become a good friend and more later on.
Brave has 1:3. However, this is Pixar's first movie with a female protagonist.
Film - Live Action
The casting for The Avengers is even less balanced than the Sixties teams. While the original team had a 4-1 ratio (Hulk left almost as soon as Cap joined) and the second had a 3-1 ratio, the movie's inclusion of Fury and Agent Coulson as "title" characters put the central cast at 7-1. Needless to say, some chunks of fandom took note. Maria Hill was added to adjust the ratio a little.
Joss Whedon himself was not happy about this, and has said he chose to add Scarlet Witch to the sequel partially for this reason. Meanwhile, the Marvel Universe LIVE! stage show (which was inspired by the movie and the MCU in general) added The Falcon and Captain Marvel to the team to help offset the racial and gender disparity.
It's very common in the Marvel Cinematic Universe in general. Just like Avengers, the Guardians of the Galaxy also have exactly one female teammate (Gamora) and Thor's friends are the "warrior three" and one female warrior (Sif).
Jennifer Parker in the Back to the Future films. Robert Zemeckis and Bob Gale say that had they intended to do a sequel at the time they made the original film, they would not have put "the girl" in the car at the end. Sure enough, in the second film, she's sedated less then five minutes in and pretty much spends the rest of the series that way.
Bimbos in Time inverts this by having only one male character in the hero team (referred to as "the male Bimbo"); indeed, the only other male character with a major role in the story is the villain.
Outside of the secretary that hits on Steve and out of all the support crew for Captain America, Peggy Carter is the only significant female member of the SSR's personnel. She, however, is arguably one of the main characters of the movie, though.
The Smurfette Principle was dissected and explained with disturbing precision in Donnie Darko as being a non-existent issue, because all Smurfs are asexual. While it's true that they reproduce by stork, this doesn't stop them from falling in love with Smurfette. More on this issue in Comics, above.
In Fight Club, Marla Singer is the only major female character — Fight Club itself is entirely male. On the commentary track, Helena Bonham-Carter talks about how she was glad when the support group scenes were being filmed because it was effectively the only time there were other women on set.
The movie is about universal frustrations. By portraying these frustrations as male and implying that few females could relate to it, it invokes the trope even further.
The movie is in fact concerned with male frustrations, being narrated by and about a frustrated and idealised masculinity. Specifically, how modern consumerism has an inherent effeminacy (e.g. "the Ikea Nesting Instinct" & "we used to read pornography: now it was the Horchow Collection..."), versus the classic masculinity of the pre-historic "hunter / gatherer" ideal that Tyler Durden advocates. The Gender Binary is destabilised both by the sexually aggressive, non-feminine Marla; and Bob who has his testicles removed and grows breasts. The Narrator (and therefore Durden) are consumed by the implications of (post-)modernity for the masculine subject, hence why the Fight Club is male only.
Galaxy Quest parodies this on Star Trek (see Live-Action TV below) by having only a single female character on the show, whose actress was constantly annoyed that her only roles on the show were Fanservice and repeating the computer.
At the end, when the show is revived, Laliari joins the cast
The Toho films are notorious for this. Throughout their famous Kaiju (specifically Godzilla) film series, only 6 monsters have been explicitly female. These monsters are Mothra, Rodan (one of the monsters in the original film was a female), Manda, Kamacuras (arguably, since there is more than one), Megaguirus, and Biollante. This becomes especially evident when one begins to wonder where the heck Godzilla's son came from. Some fans believe that Destoroyah and Kumonga are female, but that has never been confirmed by Toho. The original Japanese films are ambiguous on the manner, because they never refer to the monsters with gendered pronouns; all the monsters, even Godzilla, are referred to as an "it".
In the British Godzilla knock-off Gorgo, the monster (the big one at least) is female, but there are no female human characters at all. In the Mystery Science Theater 3000 version, this made it difficult for the bots to complete their "Women of Gorgo" calendar.
All three main characters in The Hangover films are male and so are nearly all substantial supporting characters but Jade from the first film comes closest to being a female lead. The second film effectively has no important female characters in terms of screentime - even Stu's fiancee has only a few lines.
In Immortals, Athena is the only female god seen in the entire film. Phaedra is also the only female travelling with Theseus.
Inception has a crew of around six guys and one girl. There is one other important female character, and for most of the film, she's a projection of the main (male) character's subconscious.
Other than her mother's brief appearance early on, Isabelle is pretty much the only female character in Jack the Giant Slayer.
In The League of Extraordinary Gentlemen (both the film and the graphic novel), Mina Harker/Murray was the Smurfette in the otherwise all-male League. However, she is by no means The Chick — she is the League's leader in the graphic novel. In the movie it's made clear early on that she's a vampire who can kick all the other League members' collective asses. Alan Moore said he titled it "Gentlemen" to reflect the sexist tendencies of Victorian times.
In The Film of the Book as with the book, The Lord of the Rings has very few female characters. The film tries to combat this trope by giving Arwen the roles of Glorfindel and her brothers Elladan and Elrohir, and writing up her part in other ways. However, by cutting out the whole Tom Bombadil section it also leaves out Goldberry, one of the few other female characters.
In the Ralph Bakshianimated version, the only female character with a speaking part is Galadriel. The only others to even appear are Éowyn (who gets a few seconds of standing behind Théoden's shoulder) and a pair of unidentified women in the background of The Prancing Pony.
This is also almost certainly why Galadriel turns up in the film of The Hobbit, when she does not in the book. The second (and probably the third) part of The Hobbit introduced a completely original female character, an Action Girl elf woman named Tauriel, so that there would be at least one prominent woman in the story.
In Marianne, Marion Davies, playing Marianne, is the only female with a speaking part.
The Matrix Trilogy is an interesting case. True, Trinity is the only female in the main group of characters throughout the trilogy, but incidental characters are far more likely to be female.
In Mean Girls, the two Mathlete teams we see each have a single female member, presumably because of the double-funding incentive Kevin mentions.
The Men In Black don't have many female agents. The end of the first film shows agent L, a woman who becomes J's new partner. However she is neuralyzed between films and given a Written-In Absence to make way for the return of Tommy Lee Jones.
With the exception of Kelly, the female characters in Mystery Team play very little part in the story, and are only in a few scenes each.
In The Naked Spur, Lina Patch (Janet Leigh) is the only female in the five-person Minimalist Cast. Her obvious sexual desirability is used by the bad guy, a fugitive who's been caught by a bounty hunter, to sow tension between the bounty hunter and the two partners the bounty hunter got stuck with.
Oceans Eleven and, for that matter, essentially every crime movie with an ensemble cast.
The second movie averts it by bringing in Catherine-Zeta Jones, and the third movie plays it straight by dropping Julia Roberts and Jones and bringing in Ellen Barkin. It should be noted that all three of these women were a love interest for one of the main (male) characters.
Pacific Rim has roughly 9 major characters, only one of which—Mako—is female. She's more assertive and plot-relevant than most examples, has her own story arc, and isn't presented as a Love Interest despite some Ship Tease with Raleigh. Sasha could have made the movie an aversion if she'd had more screen time and if she hadn't been swiftly killed off via The Worf Effect.
In Predators, Isabelle is shown to be the only female cast in the entire film.
In the original Predator, the cast was made up of a bunch of battle-hardened marines and one female prisoner-of-war whose primary function was to create an Enemy Mine situation.
In Red, Victoria and Sarah are the only female characters in the team, and Sarah is not even an official member, being a civilian who was caught up in the mess along the way.
Dorothy Lamour in the Bob Hope/Bing Crosby "Road to ..." movies (Road to Morocco, etc). Roger Ebert referred to "Dorothy Lamour Syndrome" in his Little Movie Glossary; when two men and one woman have a dialogue in a movie, the woman is usually reduced to looking back and forth between the two men as they talk. Lamour had an excuse, as Hope and Crosby were frequently off-script and adlibbing.
Salt was the only known female CIA agent and Russian spy.
Star Wars: Leia is the only major female character in the original series, and Padmé is the only major female character in the prequels.
It affects the merchandise, too. Toy producer Hasbro has always been reluctant to make action figures based on Padmé's various gowns, but have settled for releasing one a year. It's somewhat justified by the fact that most of Padmé's outfits don't easily lend themselves to action figures. But if Alien Extra #5 is getting a toy, well...
After the There Is Another line in The Empire Strikes Back someone suggested to Mark Hamill that the mysterious second Jedi might be Leia. Hamill joked that she had too much power already. "She's the only woman in the universe! If you don't make it with her, you're a monk!" An early draft of the script for Empire, written by Leigh Brackett, included Luke's twin sister — who was not going to be Leia, but instead another Jedi, already in training on some remote planet. This idea was never developed, though the "There Is Another" line might be a reference to it.
Return of the Jedi was originally to include shots of several female Rebel pilots in the attack on the Death Star, with at least one getting a substantial amount of dialogue, but for unknown reasons these shots were all removed from the final cut. The one line of female dialogue that remained in the scene ("got it!") was over-dubbed with a male voice.
In the 2011 J.J. Abrams' film Super 8, Alice Dainard is the only female in a group with 5 young boys making a film and navigating their way through their adventure. In fact, she's pretty much the only female in the entire movie, other than one of the boys' mothers.
Sif is the only Action Girl in Thor's gang of warriors. This is lampshaded in the film, where it is noted that Sif is the only girl in Asgard to want to become a warrior, and must do so in the face of entrenched sexism. Anyone who knows about Norse history or mythology will find this odd, since Scandinavian women enjoyed more freedom than women almost anywhere else in the world during the medieval period, and Norse Mythology features several Action Girls.
Depending on the medium. In the film itself there are three female Autobots: Arcee, Elita One and Chromia. Arcee gets the most screen time and the line, but the sisters do get a good fight scene with Sideswipe at the beginning. In the novel and comics Arcee is the central component with Chromia and Elita One as drone units she controls and they can combine into a larger robot.
Arcee was cut at the last minute from the first movie and was replaced by Ironhide because of negative fan reaction to her. Also, it was decided that there wasn't enough time to discuss why there were female Transformers in the first place (not that it stopped them from appearing in the second movie). There are a handful of female human characters, though most are simply eye candy.
In the 2010 film The Traveler, Jane Hollow is the only female police officer present in the film, and the only female who took part in the assaulting of the drifter 1 year prior to the story.
Notice that before the 60's, almost all film adaptations of classic adventure novels by Verne, Wells, London, Rider Haggard, etc... try to shoehorn a lady even if the original literary work had no use for them.
Noob has a decent number of female members, but the titular guild spent time with just one woman early in the work's run before introducing its female Honorary True Companion. The fact was blatant in the webseries, but the first installements of both the novels and the comic made sure to introduce the Honorary True Companion before the end. The two elite teams both have only one female player and a male Sixth Ranger, plus one of them took in its male Team Wannabe over the course of the series. One of these teams got a second female member, but only in the novel storyline.
Atalanta was the only women on board the Argo in Jason and the Argonaunts. Some myths state that Jason refused to allow a woman on the ship, which meant that Medea would be the only woman on the voyage back.
Of all the gods and goddesses in the Roman pantheon, Venus was the only one to have a planet named after her.
It wasn't always like this. Originally, the six planets were Sun/Sol (male), Moon/Luna (female), Mercury, Venus, Mars, Jupiter, and Saturn. Two out of six isn't that bad. After Sun and Moon were removed, the next planet that was discovered was named Ceres, also female. So for a short time two of five planets were female. Ceres was later demoted into an asteroid, just like Pluto a few years ago.
Dwarf planets avert this. Of the five most recognized, three (the aforementioned Ceres, Eris, and Haumea) are feminine. Similarly, moons are more often female than male, with many of Jupiter's moons being named for his lovers (but there's still some guys in there).
It's worth noting that many pantheons that assign a gender to the Earth itself make it female, including the Roman Terra, which is occasionally used as the "proper" name of Earth.
Barely averted in Bugs Bunny's Birthday Ball; Honey Bunny is the single most prominent female character, but she's also accompanied by She-Devil on the playfield.
PPVs also fall victim to this since there will often only be one women's match per PPV (apart from Night of Champions when they had two titles so they had two matches; they skated around this in 2010 by having the unification match at Night of Champions) and indeed, as is often the case on the regular TV shows, a mixed tag match will often be counted as the token women's match despite the women usually taking a backseat in those matches. There have also been a few PP Vs in which there are no women's matches at all.
This is especially glaring in WWE where of course there are far more men than women on the roster with several different divisions devoted to the men while having a separate single women's division. For a while they had two different titles for the women (one for Raw, one for Smackdown) but they have since been unified leaving the women with just one title to fight for.
In TNA they have a singles and a set of tag team titles for their women but in contrast to WWE, not enough women on the roster to have full fledged divisions for both. Indeed for the majority of 2010, the same woman (Madison Rayne) held the singles title and was one of the tag champions. While she was built up as a strong singles champion, the tag titles were mostly forgotten about and three months went by without the belts being defended at all. When new champions were crowned, one of them actually did not appear on TV at all after winning them and left the company a few weeks later while the other appeared once before also leaving.
It's a problem in both WWE and TNA that each episode of their show typically features one women's match. Often, Impact and Raw will feature two women's matches (usually the three hour Raws where there is more time) but mismatched rosters means that Smackdown has about five women while Raw has about eleven and in 2010 most of the time the women were only featured in backstage segments on Smackdown since they had to avoid being too repetitive with matches. Then of course there's the odd time where there won't be any women's matches at all. Since the advent of the "Supershow" format, no divas matches on RAW and SmackDown are becoming the norm as the WWE tends to focus on its more popular male wrestlers like John Cena, Sheamus, Randy Orton, Alberto Del Rio, The Big Show, Kane, CM Punk, Triple H, and Daniel Bryan; who provide huge TV ratings and are more over with the WWE Universe than the Divas (with the exception of Vickie Guerrero, of course).
Raw is a big offender since the most the women usually get for a segment overall is on average five minutes at best. 2010 had an outrageous series of weeks where a match was one minute long, the next week 50 seconds and the week after that less than 20 seconds. Though on the 3 hour Raws, the women will usually get more time for matches.
Rectified on the B Show, at least after it has been established and main eventers give way to those who need more screen time. Women get as much time to wrestle here as the men and promos as backstage segments are rare.
In fairness though, while episodes will normally feature only one match, WWE and TNA do generally try to feature all their women on TV regularly. There have been cases where multiple storylines for the women have taken place at the same time with backstage segments and pairing the women with male Superstars. WWE have recently been quite good at making sure all their Divas are featured on TV regularly (without throwing them all in a multi diva tag match). NXT has been a big help with this, as is WWE Superstars and WWE Main Event.
Dead Ringers featured a primarily male cast, with a single female member. This allowed the male impressionists to stick to the impressions they were good at or otherwise fitted their voices (and on the TV adaptation, appearances), while the sole female impressionist had to be three times better because she had to do ALL the women.
When Sandi Toksvig first appeared on I'm Sorry I Haven't A Clue in the 1990s, she remarked how proud she was to be 'in the long line of women who have appeared on the show' (she was the third, and the show had been running for about twenty years at that point.) This provoked considerable laughter from the audience, and a sort of 'oooh' noise from Tim Brooke-Taylor.
Betty Marsden was the only female performer to appear on Round the Horne and it's predecessor, Beyond Our Ken.
The Brewing Network's Justin tries hard to make sure there is at least one woman on The Session- usually it's the chat moderator, with the role mostly filled in the early years by Daniela and afterwards by Beevo. Occasionally Suzie Q would join the crew. Listeners have criticised the show as being overly blokey as a result. The other shows are almost always 100% male, though Beevo occasionally makes a contribution to The Sour Hour, as she is working at The Hop Grenade while the show is recorded.
The Dino Attack Team in Dino Attack RPG has had 241 named agents over the course of seven and a half years, out of whom only 20 are female. While we're at it the medicinal department has fifteen major characters out of whom only four are women. There are still a number of female NPCs outside the team, though.
Most action toy lines in general follow this trope, generally on the basis that boys won't buy action figures of female characters. This was the reason Katara from Avatar: The Last Airbender never got an action figure despite being an Action Girl on the main cast, while a male character, Bumi, who was only in one episode, got one. Howver, there were a far share of males who missed out on figures, like Iroh and Ozai, and a live-action Katara was made.
Before they became animated series, the G.I. Joe and Masters of the Universe toy lines debuted with a single female character each (Scarlett and Teela, respectively). Each added a female villain before long (The Baroness and Evil Lynn). For a while G.I. Joe added one woman per year, plus variations on the existing characters. Masters of the Universe added...one.
Although Masters of the Universe eventually spun off an entire Distaff Counterpart franchise, She-Ra: Princess of Power, which featured only three MALE characters amongst an otherwise all-female cast. (And two of those males, Kowl the owl and Loo-Kee the elf, were pretty androgynous anyway.)
In BIONICLE, every major Toa team is composed of five males and only one female. The same goes for the Matoran villagers; the story focuses on six One Gender "Tribes" of Matoran but only the tribe of water is female, and consequently all but two female characters are coloured blue. To make this even worse, most villainous groups of six, such as the Piraka or the Barraki, are entirely male. More Matoran tribes exist and are mentioned in the Expanded Universe: eleven male tribes, three female (Water, Lightning, and Psionics), and a tribe of Light composed of both genders (for what it's worth, the tribe of Plant Life was intended to be female, but a typo set the tribe's male status in stone forever). So it took a while, but the ratio is now somewhere around four-to-one and therefore slightly more balanced than the main ensemble tends to be.
When the focus shifted to the Agori race on another planet, it was established that their tribes don't have the one gender rule. In theory, there can be more females than there were before since no one tribe has to be malenote though later story material revealed that the Rock Tribe does banish its women, and said females could be of any tribe. In practice, only one female character was introduced as a set in the one-and-a-half years of this story... and she was still the blue one. Supporting material discusses this somewhat — the story arc in question focuses on arena gladiatorswith survival of the race as a whole at stake (not the most feminine profession) and it's mentioned that female gladiators are generally less common because the villagers are less inclined to put their faith in female gladiators, which they perceive to be weaker. Of course, said sole female gladiator introduced really isn't at all fond of the sentiment.
Hero Factory has a worse case of this, with the core group only having a single female character, Natalie Breez, and most of the villains also being male. The backstory does attempt to even out the ratio, but these toyless characters are still usually placed into insignificant and often stereotyped roles — the entire Hero Factory telephone operator staff is made up of fembots, and the Animated Adaptation also introduces a typical bitchy TV-reporter. Since all characters are robots, perhaps their "gender" is specifically designed to fit these roles.
In Life on Mars, an older theme from the Turn Of The Century, there is exactly one female character: Cassiopeia, a female Martian (distinguished from the others by her eyelashes).
LEGO's "Minifigures" series has received criticism for only having two female minifigures per series of 16. It doesn't help that they're stereotypes like cheerleaders and nurses.
...and surfers, snowboarders and cavewomen.
LEGO themes in general get this pretty badly - compared to most, BIONICLE actually had it downright good -, to the point that the fanbase tends to get excited by the female minifigs of the Minifigures series so that they can actually have a slightly more feasible number of females in their city setup or whatever. Hell, the theme which had the best ratio was probably the Harry Potter licence, and even it downplayed every female except Hermione (with the next-most important female character, Ginny, only appearing in three sets across the decade of the line's existence; anyone else is lucky to get more than one). When The Clone Wars animated series came along, LEGO's Star Wars licence also started doing a better job with more frequently occurring female minifigs; before that, any female minifig besides Leia was something of a rarity, and even Leia was an uncommon occurrence. In fact, Padme only popped up in her handmaiden disguise until a minifigure of her in her queenly garb appeared in a 2012 set.
There are around two or three females in Visual Novel Morenatsu, none of which have in-game sprites.
Chain of Hearts tends to have a large imbalance of the male-to-female ratio. Granted, there are plenty of female characters (as the cast is massive), though this is overshadowed by the fact that the most powerful characters are male.
Inverted in "The Watchers" arc. The title organization has about nine members, and only one of them is male. He's the second-in-command, and is often teased by the female members for being the only guy. But this is probably the author's subversion and attempted attack on the Smurfette Principle. It seems to go against the themes of previous arcs, but The Watcher arc is written by a different author (the other arcs alternate between three other guys). Oddly, the author behind "The Watcher" arc has a tendency to make fun of the other three authors by writing characters that are presented as male at first, but turn out later to be female...
Anita Sarkeesian of Feminist Frequency tells Hollywood that it is in fact possible to have more than one woman in your script. You could even have 2 or 3 women or even the majority of your cast be women.
Homestar Runner has Marzipan as its only female character. The fact that it uses such a Minimalist Cast makes her the only female character in the universe. She lampshades this fact in the page quote, found here. The creators of have repeatedly tried to add another female to the cast, but have never been satisfied that they've found a good enough concept to justify it, aside from the sake of adding another girl. This was spoofed in a special feature on the "Everything Else vol. 2" DVD, Why Come Only One Girl?.
The commentary to Why Come Only One Girl? points out that Teen Girl Squad eventually became their "new female outlet".
The Cheat Commandos, as a parody of '80s cartoons, do this explicitly with "Foxface", whose action figure boasts "Lady Type!" and "Not One of The Guys!!" The latter is a direct reference to the token females of G.I. Joe. Even then, Foxface has never had a speaking part (though Crack Stuntman's girlfriend got a brief speaking part as a character in one episode.)
In Red vs. Blue, Tex is very much aware that she's the only girl, until another is introduced in the fifth season. She also gets notably huffy when Donut is mistaken for a girl because of his new pink armor, and her teammates imply that she's not a "real" girl. She's also, undoubtedly, the biggest Bad Ass of the show.
The trope is discussed in GEOWeasel, and referred to as "the law of webtoons". The same episode introduces the main female character, Sapphire, who is the only female character to appear for a while, though some later episodes feature Cass along with Sapphire before the series goes back to Sapphire being the only girl.