In total, there was a whopping total of forty-one main cast members in the history of the show. And that doesn't even count all the recurring characters that appear throughout the series.
American Horror Story: Has a huge amount of characters per season. Since the series is an anthology, each season brings in a whole new cast.
Babylon 5: Had no less than 11 characters listed in the opening credits, counting all seasons together, with a fair amount of turnover from one season to the next. This is not counting the large number of semi-important characters that didn't make the opening roll.
This show is notable not only for the size of its cast (with knowledge of over 20 characters required for even basic comprehension) but for the sheer number of named recurring minor characters, many of whom have been with the show ever since the miniseries. This may be a function of the show's premise: as replacement officers are in perishingly short supply, the Galactica naturally has a very low staff turnover rate.
Tricia Helfer in herself plays Loads And Loads Of Characters. All the Significant Seven Cylons have many copies, such as Number Eight's Boomer and Athena, but Number Six has more distinct and/or significant copies than any other model. Yet Tricia only gets one salary.
The Brady Bunch: The original show had 9 main characters. The Reunion Series The Bradys had all of those plus each of the six kids in the original had wives/husbands/ boy/girlfriends/ kids of their own added to the mix. No wonder it was an hour-long show!
Usually kept a good rotation of older characters being killed or otherwise taking a bus, but the last season saw an influx of potential slayers and that number came to about 25 or so.
As of the comic continuation Season Eight, there are around 500 Slayers in Buffy's expanded group.
Carrusel: Had a classroom of 20 kids, their teacher, at least 4 other teachers, the principal, the groundskeeper, the kids' parents (most had both), siblings of various kids, and a lot of other friends and random people involved in random plotlines.
Community: Has quite a few. Aside from the 9 main characters (the study group, the Dean, Chang) there must be a dozen or more recurring named characters throughout the series. Leonard, Starburns, Professor Professorson, heck, every professor they've had in their "main" class that they all take together throughout the show, only to name a few.
Deadwood: By its third season, this show had at least thirty "regular" characters, most of whom actually did appear in every episode.
Degrassi: The current incarnation began with 13 title characters, 7 recurring, and 1 regularly mentioned unseen character note 20 or 21 depending on if Heather Sinclair counts. Due to the focal point being a school, the cast naturally shifts around, some leave, some join, lots of bus rides and mysterious disappearances. As of Season 10 only one title character from the original season is left in the opening credits, but the series now boasts 22 title characters, 14 recurring... and one regularly mentioned unseen characternote 36 or 37 if you count Heather Poulette. For those keeping score at home- note The series has had 54 main characters, over 50 recurring without a bump up to main character, and two ghosts named Heather.
Doctor Who: This show is fifty years old and has a ridiculous amount of characters. Thankfully, at one time you'll only need to know about maybe five or six max (the Doctor, his companion(s), and any family/friends/recurring characters), plus the one-shot characters for a single episode. But if we were to list every 'main' or major-supporting character the show had ever had, we'd be here all day.
Downton Abbey: In its first series, this show had twenty major characters who appeared in every episode, with an additional five recurring characters appearing in two to four episodes. Series two is promised to add a least one new regular and three heavily recurring characters.
ER: Accumulated quite a few over its 15-season run, with the main billed cast never going under 10 or so. Although they were pretty good about writing characters out and in properly, except for Ramano where they Dropped A Helicopter On Him.
Farscape: Had accumulated so many main characters by the third season that the writers had to split the crew into two parties, both of which had a copy of the protagonist John Crichton.
Represents nearly the whole of First Recon at the onset of the Iraq War.
This is usually true for any miniseries that focuses on the military, such as The Pacific and Band of Brothers. In The Pacific the focus is three different men from three different companies, all with their entirely different friends, families, commanding officers, etc. featured. The large cast was also one of the few criticisms Band of Brothers received when it was first aired, even though the 25 or so men that make up the main cast is a relatively small number compared to the amount of soldiers that are featured in the book and were a part of the company in real life.
Gilmore Girls: Had around twelve main characters plus many recurring ones, some of whom were very popular (Mrs Kim, Lucy, Olivia, Kirk, Taylor, Jackson, Zack...). They managed to get most of them together for the finale (though no Paris, Christopher or Logan - they'd all had their series wrap on the penultimate episode).
Gossip Girl: This show is approaching this. You have the main cast (Serena, Blair, Dan, Nate, Chuck, Jenny, Vanessa), the parents (Lily and Rufus, mostly), Georgina, Eric, whoever Serena's "Boyfriend of the Month is", Gossip Girl herself (as omniscient narrator), Penelope and the Mean Girls (3 of them), Dorota, Olivia Burke (if they bring Hilary Duff back), Eva and Juliet Sharp ( both of whom will no doubt be a big part of the entire 4th season). That's 21, and that assumes they don't add anyone else from their colleges, which is unlikely. Soap Opera, indeed.
Grey's Anatomy: The cast got so big that recurring characters like Nurses Tyler and Olivia and the Chief's secretary completely disappeared. They even killed off Mer's mom, George's dad and put several main characters on buses in order to cut down on the amount of people we have to keep track of....
Harper's Island: Had a bad case of this, mainly because it's a murder mystery and they needed lots of people to die. Out of 29 characters who were murdered, we never really got to know a dozen or so of them.
Heroes: Right off the bat. Much like LOST, Heroes also has a high character attrition rate.
JAG: Had as many characters one would expect for a 10 year series.
Did this on a regular basis. The Muppet Show, Fraggle Rock, and Sesame Street have all featured core casts of at least seven to ten main characters, another ten or fifteen secondaries, and dozens of recognizable recurrers.
For obvious reasons. A live-action show will probably find it cheaper/easier to hire a new actor to play an extra or bit part rather than track down the guy who was in that one episode seven seasons ago, whereas a puppet show will almost always find it easier to pull that old puppet out of the closet. Helps that a lot of the voice actors were men of a thousand voices.
Check the 40-years of this show (1971-2011) and you'll typically find that the bigger the list of Riders in a year, the more non-Rider characters there's gonna be. Kabuto (11, including the 3 Movie-Only Riders) and Ryuki (13, 14 including the Decade-only Rider Abyss) show this off well.
And now it goes Serial Escalation - with a whopping 486 confirmed costumed characters on screen, not only is this the biggest collection of characters ever, Toei has even sent this to the Guinness Book Of World Records for the biggest number of suited stunt actors on screen.
Has had twenty-eight credited cast members in total, with about twelve to seventeen being a part of the cast at the same time, due to the Anyone Can Die factor. That's not even counting the large stable of important secondary characters, nor the dozens of smaller recurrers.
To give an example: season four starred sixteen people. There were twenty two important recurring characters, some of whom appeared in nearly every episode, and numerous recurring, named Red Shirts and Mauve Shirts like Keamy's team. That's not even counting the sheer number of important one-off characters who will probably come back later or the random friends and family members of the Oceanic 6 who came back in the finale or the dead characters who appeared in flashbacks or visions or the stranger ones like Jacob.
Lost has reached the point that it's nearly impossible to jump in to the show having missed a few episodes. Even if you followed the story from the beginning, if you miss 3 or more episodes you'll come back to the show to find a brand new character referencing another character you've never heard of before. Even once you figure out this new character, eventually (probably during a season finale) another character you've never heard of will show up accompanied by dramatic reveal music as the main characters look at them in awe...it turns out that the new character was introduced in a dream sequence in the episode you missed and is crucial to the plot.
Mad Men: Not only has the large number of employees at Sterling-Cooper as regulars and semi-regulars but also has multiple episodes involving into Don's harem and home life, Betty's circle of friends, and the personal lives of Sal, Joan, Pete, Peggy, Roger, and Bert, and Harry.
NUMB3RS: Fits the bill. While the core duo of Don and Charlie appear in every episode, and characters like Colby, David, Alan, and Amita are almost always present, there's a revolving cast of other characters who are so known to the audience that their appearance is nothing special, but who still don't make it into every episode.
Once Upon a Time: Due to pulling characters from every single fairy tales, this is pretty much a given.
Oz: During any given season, there are about 15-20 recurring characters that are prisoners, and that's not even counting the prison staff.
Power Rangers: There are somewhere around 106 people who count as the eponymous Rangers alone, then add in at least 15 distinct sets of allies, supporting characters, and villains. If you count the 17 years of weekly monsters, you have a cast of thousands.
These promotions, by their very nature, tend to have this. After all, ideally, you want the fans to care about every match, and when the shows run 3+ hours, that's a lot of matches.
The annual Royal Rumble Match (held the last Sunday of January every year) is a good way to bring all these characters together. Thirty (forty in 2011, and twenty when it began in 1988) wrestlers compete in the match over the course of about an hour, and typically only about ten of them will be recognizable to casual fans. Even WWE diehards may have trouble keeping track of all the cameos. Remember Daniel Puder? Probably not - but if you're a Royal Rumble connoisseur, you do.
In 1987, Jim Crockett Promotions took over/bought (Nobody seems to know which is the absolute truth) Championship Wrestling from Florida and bought the Universal Wrestling Federation. This gave them four more hours of TV to fill each week. While there were three distinct and separate crews, wrestlers would move over constantly. Late in the year, the UWF shows stopped having their own crews while CWF kept losing importance. At the end of the year, the UWF shows were the same as the JCP shows with different names/intros (UWF was the same as NWA Pro Wrestling and Power Pro Wrestling was the same as NWA World Wide Wrestling. The announcers would only mention "The Wrestling Network" during the shows.), while CWF's B-show (Southern Pro Wrestling) was cancelled and CWF became a NWA Pro Wrestling with localized commentary and a different name/intro. UWF disappeared as 1988 started, PPW disappeared a few weeks later, and CWF stuck around for a few more months.
In 1998-1999, WCW was so bloated that it had over two hundred wrestlers under contract. Things were so mismanaged that some of these wrestlers were never even used on television and essentially got paid for sitting at home doing nothing.
This was deliberate on WCW's part (which, arguably, make the situation even worse). The idea was to sign up every "name" wrestler that became available, right down to the C-List Fodder, in order to deprive the WWF of the chance to sign them themselves. The company signed many lesser stars knowing they had no intention of putting them on television. A workable theory for a company backed by Uncle Ted's billions, but the sheer number of wrestlers on the payroll became unmanageable. Former WWF star Honky Tonk Man had a brief stint in WCW where wrestlers were paid for each show they showed up at, even if they didn't actually work. Attendance was taken by writing your name on a timesheet, but nothing more than that. He quickly caught on and simply stopped showing up, having a friend of his write down his name in his place. Reportedly, management didn't catch on for almost a year.
Any show where the producers think it's a good idea to introduce new competitors half-way.
Such as the 2007 UK series of Big Brother, which, thanks to a mix of poorly-planned twists, disqualifications and walkouts, had a total of twenty four housemates.
Revolution: The cast consists of 12 characters who qualify as main characters. Then there are 19 characters who at least qualify as recurring characters. There are at least 83 minor characters with actual names. As you can probably expect, a large number of these characters get killed off, put on a bus, or just mysteriously disappear. Also, this is only for the first season. There's no telling how the numbers will change in the second season.
Robot Wars: While this show generally only has a dozen robots per episode, counting the house robots, once you realise that there are about a hundred competitors, maintained by roboteer teams of at least three people, the total number of faces in a single series is incredible.
Saving Grace: Although this show is primarily about its title character, the show features about a dozen main supporting characters, and another couple dozen recurring minor characters. All are well-written & well-acted.
Scandal: This series has ten main characters going into its third season. There are also various supporting and recurring characters.
Has a huge expanded cast of recurring characters, the most famous one being Janitor who was technically a guest star every episode of the first season. Among the major guest cast is Nurse Laverne, The Todd, Keith (who managed better than most of Elliot's long-time boyfriends), Doug, Ted, Lonnie and a few more that aren't quite as frequent like J.D.'s brother Dan.
Then there are the "Third Tier" of characters, who started the show as background extras or crew cameos. Listen to the commentaries on the Season 2 and 3 DVDs, and one can hear jokes about the crew nicknames given to recurring extras, like Dr. Beardface, Snoop Dogg Intern/Resident/Attending and Colonel Doctor.
The show also regularly expands its cast every year, with new interns.
Started off with quite a few characters - just the Gallagher family itself is large - plus their neighbours and some supporting characters. The Maguires then joined in season 2. Supporting characters would also get their chance in the limelight every so often...this troper has always been a fan of Lillian!
This being the Chatsworth Estate, most of the original characters (as of season 9) probably wanted to get away from the area, and now the only original characters left are Frank and Karen.
Skins: Has a new cast every 2 seasons. Considering there are 8 or 9 major characters per season, and then you add in all their family and other acquaintances...yeah, it's start to get confusing after a while.
According to the Smallville wiki, throughout the series there are 18 main characters, 170 recurring characters and 341 minor characters, with a total of a staggering 529 characters. Not to mention some closely-related minor characters are merged into one page, for example the 4-man Insurgence team, the two Disciples of Zod and the 3 Weather Girls, meaning the count should be even higher.
Sons of Anarchy: Has at least a dozen members of the titular motorcycle club as main characters, but then you add in their families, law enforcement, rival gangs, other chapters, the entire Irish subplot, and miscellaneous politicians and citizens of Charming, and you have a huge cast, most of which can reappear at any time.
The Sopranos: Gradually became this, with upwards of 20 actors listed in the opening credits (in the episodes in which they appeared) and at least as many significant recurring ones. Some, like Bobby and Agent Harris, started as minor roles and grew more significant over the course of multiple seasons. Even at the rate at which they were weeded out, jumping from the end of season 1 to the beginning of season 5 or 6 would have to be pretty bewildering.
Star Trek: Deep Space Nine: Had a cast of 7 regulars (admittedly, Cirroc Lofton AKA Jake Sisko didn't appear that much later on) all of whom were very well developed. However, the show had an enormous set of secondary and tertiary characters, many of whom were just as developed, if not MORE developed than the main cast. Gul Dukat and Garak in particular were very deep characters despite not being part of the main cast. Since the Deep Space Nine regulars were for the most part (if not all of them) more developed than the main cast of other Star Trek series, it follows that even the Deep Space Nine guest stars were more developed than the main characters in the other series.
Spoofed by this sketch comedy show which presented a fictional TV program called "Just the 160,000 of Us." It was presented as a soap opera where the aforementioned number of people all somehow shared a house, and all of them had their own subplots.
Similar in the German comedy Switch, with the fictional soap "Alle und wir" ("everyone and us"), which seems to have hundreds, if not thousands of characters... although we only see six of them, and a seventh one (Robin) is mentioned.
St. Elsewhere and Hill Street Blues: The large ensembles of these shows led MAD to run a very crowded single-panel gag featuring both casts.
Steven Bochco: This guy was famous for making TV shows that had a large ensemble cast, including L.A. Law and Hill Street Blues. He also had a few clinkers including Cop Rock.
Supernatural: Has several dozen recurring characters (most of whom have at least one episode that heavily features them). However, pretty much all of them are dead or Put on a Bus by now, bringing the number of characters in the main cast down to a more manageable number.
Super Sentai: Has 199 heroes (including the 6 Gokaiger and AkaRed) as of the main 35th Anniversary movie this year, with 35 teams over the past 36 years (1975-2011), that's counting the Core 3/5 and the 6th/Others (such as BullBlack/Magna Defender from Gingaman/Lost Galaxy). Toss in the 35 lots of villains, allies and supporting characters you'll easily hit the thousands before having to add in the weekly monsters.
Taken: This is a ten episode miniseries clocking in at about 820 minutes. It has at least 24 characters, most of whom die, are only main characters for one episode, or are Put on a Bus.
Third Watch: There are seventeen main characters listed on their trope page, alone.
Trailer Park Boys: Surprisingly, this show became this in later seasons. That Other Wikilists twelve main characters and twenty-four recurring characters. In season 7, previously minor characters like Sam and Jake Collins and Sam Losco were developed in multi-episode StoryArcs.
Has an insane amount of cast members and characters. This became especially prevalent in the third season-onwards. There is Eric's posse, Bill's allies, the opposing vampires (Russell Edgington and the like), a bunch of werewolves, Sam and his shifter buddies, Bon Temps' general population, Sookie's close friends, Lafayette's witch circle.. It's getting hard to follow at the end of season 4.
Because the show's episodes last 50 minutes, it usually gives the writers an excuse to flesh out more and more characters. In the fourth season, they had the annoying tendency to switch over to the issues that were being had by characters like Alcide - who weren't main characters at all in the novels.
Twin Peaks: Had about 20-25 major characters who were given character arcs, and about 40 minor recurring characters. This is pretty impressive considering that the series lasted only for 30 episodes, and that almost all of the major characters were introduced during the first season, which had only 8 episodes.
The Wire: By the time this show reached its fourth season it had 29 regular cast members, eleven of which appeared in every episode; they were split between the police, the gangs, the Baltimore City mayor's office and a local high school. The show also featured about 30 other characters with recurring roles. EVERY ONE of these characters was fleshed out, with their own unique arc. Nobody on the Wire is 2-Dimensional.