The very first Hell Girl episode deals with this topic, as the Alpha Bitch Yoshimi Kuroda uses hers to make her rival Mayumi Yamaguchi's life total Hell.
In the beginning of the series, Sae from Peach Girl basically had the whole school under her finger, most of the guys were head over heels for her, and some of the girls would frequently compliment her and follow her around.
Chieko has a pair of them in All-Purpose Cultural Cat Girl Nuku NukuTV. Except for one Lower Deck Episode, all they did was pop up behind her saying, "Yes, what Chieko said is right." They had names, but it only highlighted how unimportant they were; "Hidariko" and "Migiko" translate to just "left-girl" and "right-girl".
Natsumi, Minami and Kumi, the "partners-in-crime" of the Unlucky Childhood Friend Otome Katou in School Days. Otome herself is a subversion (she's popular at school, but is more of a sportswoman than a cheerleader or Rich Bitch), but boy do these four act like school bullies when they're together and poor Kotonoha is near...
Actually, these three girls are so nasty and cruel that by the end, their Alpha Bitch is more sympathetic than they are and a victim of their antics, though not as much as Kotonoha or Sekai's friend Nanami.
Subversion: Julie and Charlotte attempt to become Layla's Girl Posse in Kaleido Star to get back at Sora for being The Fool, but thanks to some bits of Character Development midway through the first season, not only they start being nicer to Sora, but they start helping Layla for selfless reasons and not to suck up to her.
Asai Yuriko, Yamano Minako, and Ayuhara Erika from Hana Yori Dango, though they don't have nearly the popularity or influence that the F4 does.
Mihaya, Miyoko and Hiroka from Naru Taru are under the "orders" of one really nasty Alpha Bitch named Aki Honda. When one of their victims, Hiroko, gets sick of it and acquires a "mon" named Oni... Aki, Mihaya and Hiroka die in very gruesome manners. Miyoko survives, but loses a leg.
Kafuko from Space Pirate Mito has a two-girl posse, who not only carry out her orders, but occasionally carry her and/or props for dramatic effect, and in one instance even gave a Noblewoman's Laugh for her.
In Demashita! Powerpuff Girls Z, the Princess' only friends are these, and once she ditched them over a fight. They then received powers from the dark Z rays, which made them posse anyone they wanted, inflating their ego and making them selfish, and when using their powers in conjunction with Princess' they actually made her stronger.
Even though they were clearly created with this trope in mind, Tenjouin Saki of To Love-Ru and her two followers are not left out of the characters given backgrounds to create decently well-rounded characters by themselves. Saki starts out as an Ojou antagonist, and then develops into her own character with her love interest outside of the main Unwanted Harem even.
Subverted in Toradora. Ami picks up a posse as soon as she transfer to the school, but they're both nice girls who get along with the protagonist clique, and even tell Ami to dial it back when she gets bitchy.
Megumi Furuta and Miyuki Sonobe from Oniisama e..., companions to Aya Misaki. Episode 30, however, gives them some Hidden Depths since they truly like and support Aya... and the Sorority seniors try to use their affection for her to their own benefit.
Heathers is named after the girl posse in the film, of which three out of four girls all have the given name "Heather". H. Chandler is the Alpha Bitch, H. Duke is jealous of Chandler's power, H. McNamara is a meek follower, and Veronica is the newcomer who actually hates being part of the group and did it solely to become In with the In Crowd.
A majority of the plot of Mean Girls deeply delved into the phenomenon.
This movie actually had two sets of such posses (actually four, if you count both male and female). On the one side for each sex was the contingent of more prototypically 1950s kids who dress like model students, act (superficially) polite, and suck up to all the authority figures they can. Then there are the Pink Ladies and their male counterparts the T-Birds, who wear tight pants and jackets, smoke, swear, play mean-spirited pranks, and generally act rude. Both cliques are shown to be flawed, but it's implied that the Pink Ladies are somewhat less flawed because they at least are honest about their shortcomings. The lesson, I guess, is that it's not really fashion or attitude that makes you cool, but a lack of hypocrisy.
Bring It On (and all of its sequels that I've seen) have the protagonist move in and out of this sort of clique.
The Final has the bitch trio of Heather, Bridget and Kelly. Heather is the ringleader and main tormentor, Kelly is her just-as-bad Dragon (although she is redeemed by the end, killing herselfover what happensto her friends), and Bridget eventually turns out to be much more sympathetic than the other two.
Jessica Wakefield and her pals in the Sweet Valley High books and TV series, and more specifically The Unicorn Club in the Sweet Valley Twins book series.
A few of these appear in Harry Potter, though they have little bearing on the plot, and usually only the leader of the group is named.
Subverted in A Hat Full of Sky: the teenage coven starts off looking like a Girl Posse to Anagramma, but gradually realise what a bitch she is, and start taking more of their lead from Tiffany, to the extent that Tiff has to persuade them to help Anagramma in Wintersmith.
The Brady Bunch: The Boosters in the Season 4 episode "Today I Am a Freshman," the group Marcia wants to join. She ultimately doesn't – in part because she failed her initiation (thanks to Peter's volcano) and because she ultimately saw that this Girl Posse isn't whom she wanted to be associated with.
Cordelia in early episodes of Buffy the Vampire Slayer had a group of yes-girls, the Cordettes, which included future vampire Harmony.
Kate and her one-dimensional interchangeable cheerleading squad from Lizzie McGuire.
Gigi's friends in Wizards of Waverly Place. They suck up to Gigi so much that they actually get plastic surgery so that their noses will look like hers.
Gossip Girl both plays this one straight (Kati, Isabel, Hazel, Penelope) and subverts it (The bespectacled Asian nerd who routinely receives the highest test scores of anyone in the school eventually becomes one of Blair's henchmen).
Paris in Gilmore Girls had her two sidekicks, Madeline and Louise, whilst she and Rory were at Chilton High.
Santana and Brittany on Glee, whose main purpose in the first few episodes was to fulfill the glee club's needed quota of 12 students and stand behind Quinn.
Community gave this trope a great sendup in the episode "The Aerodynamics of Gender". Britta, Annie, and Shirley decided to take a Women's study course for some girl time, but are taken aback when Abed says he wants to go too. A Girl Posse of 3 Alpha Bitches (One of which is played by Hilary Duff) start harassing them, and Abed quickly zings them back without breaking a sweat. Rather than thank him and call it a day, Britta, Annie, and Shirley decide they can use this to their advantage and send Abed to insult every girl in school that has ever been mean to them. Eventually, Britta, Annie, and Shirley's egos completely swell and they become the ruling Girl Posse of Alpha Bitches themselves.. Also, because it's Abed, there's a parody of Robocop in there. But Britta thinks he's saying "Rowboat Cop".
Nicely subverted on Freaks and Geeks. Vicki Applebee is the show's resident Alpha Bitch, but even most of the other popular girls at Mc Kinley High (including Cindy Sanders) have a problem with her. And Cindy, probably one of the most popular girls at Mc Kinley herself, is nice to everyone on the social totem pole .
The aptly named 'Posse' (Zuma, Redondo, and LaJolla) in Zits, although they tend to be gossips more than bullies.
Lucy, Patty, Violet and occasionally Frieda were an elementary-school version of this trope in Peanuts.
In a rare example of a gimmick that TNA has done to perfection, The Beautiful People are a perfect example of the trope in wrestling. At this point, Velvet Sky and Madison Rayne have been the Alpha Bitch and her second-in-command (prior to Madison winning the Knockouts Title, Velvet was the Alpha Bitch, but since then it hasn't been entirely clear which one is actually the leader of the group), and Lacey Von Erich in the role of the Brainless Beauty who follows the other two.
Vince's Devils, Torrie Wilson and Candice were already hanging out like best friends by the time they moved to Raw (from SmackDown!) and underwent a Face Heel Turn. They teamed up with Victoria for the sole purpose of tormenting the new girl from the Diva search, Ashley. There was some Ho Yay between Victoria and Candice and Torrie bought a dust mop dog, so she could rub its ass in the faces of their opponents.
The Minnesota/International Home Wrecking Crew in SHIMMER.
Don't you think Evolution was a sort of male Girl Posse? They wore fancy suits and Rolex watches away from the ring, and would team up to bully the likes of Kane and Mick Foley while in it. Triple H, of course, was the Alpha Bitch, with Ric Flair as a sort of "Alpha Bitch emeritus." Then I'd say Batista had the Velvet Sky/Victoria position and Randy Orton filled the Madison Rayne/Candice Michelle role.
Though it's only two people, this is still more or less the gimmick of Team Lay Cool (Layla and Michelle McCool) in the WWE.
Charlotte, Cassie, and Molly in 13 serve as this for Kendra and Lucy
Cyrano de Bergerac: This play is not set in high school, but De Guiche has the Spear Counterpart to the Girl Posse: The Cool Crowd, a crowd of hangers-on who bow to his every whim and help him victimize whomever he decides to pick on (or, in the case of Viscount De Valvert, they at least try to help De Guiche victimize Roxane and Cyrano). Lampshaded by the Marquises in Act I, Scene III, when one of them recognizes they don’t like De Guiche, but it’s best to make their bow to him:
First marquis(watching De Guiche, who comes down from Roxane's box, and crosses the pit surrounded by obsequious noblemen, among them the Viscount de Valvert): He pays a fine court, your De Guiche!
Second Marquis: Faugh!. . .Another Gascon!
First Marquis: Ay, but the cold, supple Gascon—that is the stuff success is made of! Believe me, we had best make our bow to him.
Raspberyll has one of these in the form of Asuka and Kyoko in Disgaea 3 - Of course, since the Netherworld generally counts being an asshole as a good thing, the posse's decided that they'll earn their delinquency points by being the biggest goody-two-shoes they can hope to be.
Little Busters has the softball juniors for Sasami. Each time Rin fights with Sasami, she must battle them first: they're weak, and hold half-eaten food owned by Sasami to heal themselves. Apart from this and, at one point, kicking a cat to enrage Rin, they do exactly nothing plot-worthy. Riki even refers to them as minions at one point.
Before her fall from grace, Morita in Red String had a couple of lackies— one with pigtails and one with short black hair. They followed her around and almost never said anything, but giggled and smirked at Morita's cruelty.
The blackmail ring in Ciem: Vigilante Centipede (that wasn't in the webcomic) is a Girl Posse in a college, who lets the fact that Hebbleskin-influenced Police Are Useless enable them to a reign of terror over the residential buildings at Viron University. For some reason, the campus' diversity groups are also persuaded to turn a blind eye, even when the girls commit felonies. Candi becomes a target of their wrath twice. First, they send an imposter to appear in a porno to ruin her reputation. And when she doesn't "get the message" after that, they send Wayne the Vampire to rape her.
In El Goonish Shive, Lucy and Rhoda are flunkies to queen bee Diane at Moperville South HS as seen here. Mildly subverted in Lucy's downright flippant and sarcastic manner towards Diane and Diane actually caring about Rhoda.
Subverted in Cheer! twice: The Ekaltsew Cheer team, who are shown as buffoonish and stupid would-be enemies of the Tandy Cheer team, and with Sarah and Karen, who eventually abandon their leader, Tamara, after one hare-brained revenge scheme too many.
Daisy briefly falls in with one of these, but is dumped by them later on. Subverted in that a few members of the group later reveal that the "leader" of the posse was not much liked by THEM either, so they continue to hang out with Daisy.
In Everyday Heroes, Goldie was the queen of Jane's high school. The trope is somewhat subverted in that Goldie seemed to be a benevolent despot. Jane was set to inherit the title during her senior year until she dropped out of school.
The Sisterhood of Survival of the Fittest's Bathurst High, most of them probably having about the same Alpha Bitch levels. V3 character Melina Frost's profile refers to her having been the leader of a similar group at Southridge, but this never came up.
Whateley Universe examples: at Superhero School Whateley Academy, Solange has her Girl Posse of Flicker and Fade. Hekate has her own posse of Spellbinder and Conjure until she's forced to flee from a Sidhe curse, and the Yellow Queen has the rest of the Whateley Martial Arts Cheerleaders (even though Whateley has no intermural sports teams).
Lilo And Stitch The Series: Mertle has possibly the youngest posse, who take the "parrot her opinions" duty to the extreme - Mertle insults Lilo, they say in unison, "Ye-e-e-ah."
In As Told by Ginger things are turned on their heads a little, while Courtney Gripling is the leader of the Lucky Junior High girl posse it is her second-in-command, Miranda Killgallen, who acts like the Alpha Bitch. Courtney herself is the Lovable Alpha Bitch who has several satellites following her around.
The show Angela Anaconda had Nanette Manoire and the Copy-Cat Clone Club, who, whenever Nanette came up with a plan, the first would typically say, "That's a great idea!" And the second would parrot, "Well, I think that's a great idea EVEN MORE".
Though some fanfics tend to place the cheerleaders Hope◊ and Jessica◊ as Bonnie's posse.
Avatar The Last Airbender both uses this and subverts it; Azula's posse are fully realized characters in their own right, and Mai and TyLee are not exactly enthusiastic supporters. In fact, they have largely been told by the would-be-future ruler of the world that they have no choice, Mai's boredom with life aside. Despite this, and their eventual, perhaps inevitable break with her, they are a terrifically efficient fighting force, and are wise enough to keep their ruthless leader happy, as far as she can be. To their opponents, their front must seem incredibly unified and as intimidating as any group of mindless minions, even when the target is not cornered by a locker or such.
Another (very minor) Girl Posse appears in the episode Tales Of Ba Sing Se, where they pick on Toph and call her ugly. Though Toph and Katara deal with them and send them packing in the end.
Paige Logan from Grossology is usually accompanied by a pair of sidegirls. In one episode, she orders them to floss her teeth (to their credit, they refuse).
Eve and Tori are the Girl Posse of Beth in the Polly Pocket animated movies. The pre-cutant ones, at least. While they don't have any ill feelings towards Polly and her friends and even question Beth on why she hates Polly, they let her boss them around. To their credit, when Polly's band got to play on a school event despite Beth's efforts to prevent it from happening, they decided to enjoy the show instead of put up with Beth's rants. Too bad it didn't keep them from helping her in subsequent movies.