"Lisa, ordinarily I'd say you should stand up for what you believe in, but you've been doing that an awful lot lately..."
—Marge Simpson, from The Simpsons.note (The "Lisa vs. Malibu Stacey" episode in particular.)
A child or teenager, almost Always Female, who cares deeply about all worthy causes. She wants to protect the environment from polluters, prove that women can be as good as men, and Free the Frogs. She is often the main character of the show, and spends a lot of time struggling with her idealism and whether it is too unrealistic.
Soap Box Sadie is usually a post-hippie, the sort of woman who would have been a hippie had she not been born in the wrong decade. And if it weren't for the fact that she's (usually) the heroine on a children's show and absolutely cannot be shown using drugs or engaging in "free love". (This, of course, presumes that the '60s antiwar and other activists and the "flower children" were the same people; the two groups did not necessarily overlap.)
In most shows, she exists to teach children an Anvilicious lesson about the importance of the environment, feminism, and standing up for one's beliefs. If so, expect an episode about how she shouldn't force her beliefs on others. Express them, yes, but not to shove them down someone's throat.
If she's not the main character, Soap Box Sadie is often the main character's best friend or a family member.
A variant is the angry, self-righteous activist Goth, who is much less likely to be a soapbox for the writers.
Special bonus if they actually geton a soapbox.
This character is almost always on the political Left, or at least a radical (it's worth noting that communists and even anarchists are technically not leftists by modern poli-sci standards). A character on the Right who behaves this way (and generally is much less concerned about looking "cool" while doing it) leans more toward The Fundamentalist.
Compare Granola Girl, Straw Feminist, Strawman Political, Author Tract.
Not to be confused with a sadist in a soap opera.
A male example is Lin/Lynn Kaifun of Super Dimension Fortress Macross. No sooner does he make his first appearance (during a Breather Episode in which his cousin Minmay is visiting home) than he gets on her escort, Humongous Mecha pilot Hikaru Ichijou's case for being in the military. He eventually accompanies them back to the titular spaceship/robot in order to watch out for Minmei at the request of her parents, spreading anti-military sentiment along the way. Throughout the entirety of the series, most of his time is spent either chiding the soldiers and military staff for fighting the Alien Invasion threatening Earth instead of trying to talk things out (despite the fact that most of the aliens do NOT have any intention of talking), or preaching to the civilians who call the ship home about how war and the military are bad... Despite the fact that the army is only fighting the aliens in the first place because they've been proven to be hostile.
This gets especially stupid when he is requested to join the first Zentraedi-Macross peace talks with Exsedol, and he still complains about the military and wants no part in the negotiations, despite these negotiations being exactly the kind of thing he's been wanting this whole time. Minmei, of all people, points out the contradiction.
His final appearance shows him having taken up as Minmay's talent manager on a ravaged, post-war Earth, drunkenly complaining that all the payment they received for her last show was a bag of groceries. Word of God further stated that, around the timeframe of Macross 7, he is on one of the colony fleets managing a band that is basically just a knock-off of Fire Bomber... and claiming that his is the original and Fire Bomber is the copycat.
Just to prove the main entry wrong, Nadia pretty much fits the trope and holds true to her beliefs even in the epilogue, although she does seem to act more forgiving towards people who disagree with her. Grandis DID tell her that she may end up growing out of it.
Based on flashbacks, Mermaid Queen Otohime of One Piece spent her life as one of these, constantly campaigning against her own people's Fantastic Racism against the humans (though she also opposed human racism against mermaids and fishmen) and going around harassing people to sign her petition. Her own people found her annoying, only putting up with her because she was the Queen and they knew her heart was in the right place.
Played for Drama: She's assassinated by a human, not long after finally getting people to sway with her opinions. Even in her dying breath, she tells her children not to let her death cause more anger in this world and continue to fuel the racism. Driven home when you realize that she, along with other Fishmen and mermaids, are Shout Outs to various black-freedom fighters, such as Martin Luther King, Jr., Malcolm X., and the Black Panthers.
It's even sadder because she was really killed by Hody Jones. The human 'assassin' was just the human Hody hired to burn the petitions. Hody betrayed and framed the guy to stir up anti-human sentiments.
One of the many one-dimensional characters in the old British comic Cheeky was Do-Good Dora, who always carried a placard with her latest cause written on it.
Animal Man is a rare male example of the trope, due to his ability to communicate with animals. At one point, Grant Morrison, the writer who made him that way, actually directly interacts with the character. Among other things, Morrison admits that he was using Animal Man as a mouthpiece for his own beliefs on animal cruelty and vegetarianism.
Fethry Duck in Disney comics is another male example, boasting numerous causes related to nature and society. Born in the days of hippies (1964), though long since transcended the movement. Also a male Granola Girl and eternal faddist; if not crusading for a cause, he typically has a new hobby or interest that he treats as a cause, religiously pushing it on others.
Gert from Runaways. Apparently, as a little girl, she once stole all of Nico's My Little Pony dolls because she thought that they glorified animal abuse, and when the original series starts, she's arguing with her parents over wanting to join a socialist club at her school.
Fluttershy in The Cadanceverse. As the Element of Generosity, she finds herself advocating for a variety of important causes.
The namesake for this trope is the character of Sadie Lowenstein, who had this nickname in the musical TV film Mrs. Santa Claus. Sadie was a young suffragette in 1910 Manhattan who literally got up on her soapbox (that is, she made her speeches atop a box marked "SOAP").
The main character's girlfriend in Orange County is a pretty cute use of this trope - she's always getting sentimental about baby seals, while the rest of the class try not to roll their eyes.
If you want to see a good pre-1960s example, look no further than the Marilyn Monroe classic The Seven Year Itch (1955). The main character, Richard Sherman (Tom Ewell) is spending the summer at home while his family goes on vacation. His doctor informs him that eating a lot of meat isn't healthy in such hot weather, so Richard has dinner one night at a vegetarian restaurant. His waitress turns out to be an elderly radical who tries to convert him to the cause of nudism, claiming that if the entire human race was unclothed, everyone would look alike (which of course isn't actually true, but never mind) - "all brothers together" - and there would be no more war. This offhand reference to nudity obviously serves as a Foreshadowing of what is to come, but otherwise it's something of a Big Lipped Alligator Moment. However, it does fit the trope.
Riley in Detention. Her getting whooped in her debate with Gord on the morality of eating meat triggers an existential crisis that ends with the former vegan eating a burger and trying to hang herself.
Gord himself is also one, though his views are an inversion of Riley's — he believes that not eating meat is morally wrong. That's because he's a vegetable-based alien lifeform, who is leading the invasion of Earth in order to stop vegans like Riley from eating his kin.
In Animorphs, Cassie often voices her opinions on issues she considers morally compromising. The other characters (and the readers) sometimes get annoyed with this.
In Harry Potter, Hermione's pet project is bringing attention to the ill-treatment of House Elves after seeing the potential for nastier wizards to abuse them. Apparently, most of the wizards (and most of the actual House Elves, with the notable exception of Dobby) consider it an aberration and generally aren't interested in her cause; the ones who do show interest do so in exactly that: stopping the abuse of house elves. It's the other aspect she preaches (universal emancipation and applying human labor standards like wages and holidays) that even the house elves themselves don't like.
The thing she misses with regard to their emancipation is that for most, Dobby being the standout exception, they either cannot or will not make the distinction between being freed and being sacked in disgrace; most of the other elves consider Dobby to be at least a bit insane due to his insistence on being paid, having vacations (both extremely minimal) and actually wearing regular clothes.
And she is shown to gradually come to understand and accept the fact that house-elfs actually like caring for humans and receiving nothing in return except their kindness (on that note, Dobby's desire for payment, holidays and general freedom seems to be more to do with defiance against his former masters, seeing as he refused the opportunity for too much pay note Dumbledore offered Dobby 10 galleons a week and weekends off, but Dobby requested one galleon a week and one day off a month).
Her fears are vindicated in Order of the Phoenix, as it is revealed that Kreacher's mistreatment indirectly led to Sirius' death since house elves expect to be treated like crap and are thus fanatically loyal to anyone that shows them even a sliver of kindness.
Hermione does eventually seem to grow out of the Soapbox Sadie behaviour and instead actually does something about the issues she's concerned about as Word of God says she joins the Ministry of Magic and helps eradicate laws that discriminate against magical creatures and Muggle-borns.
Main character Mia's best friend Lilly in The Princess Diaries, though she may better fit the "angry self-righteous activist Goth" description above.
In Bridget Jones's Diary and its sequel, although she's hardly a teenager, Bridget's best friend Shaz fits the trope admirably. This is especially true of the novels, where Shaz's almost constant righteous anger, expressed in politicised rants on a multitude of topics, is contrasted with Bridget's entertainingly patchy awareness of real-world politics.
A male example: For at least part of the book, Adam from Good Omens (by Terry Pratchett and Neil Gaiman, after being introduced to Age of Aquarius dogma, suddenly turns into the most militant environmentalist it's possible to be... considering he actually has the power to do something about it...
Another Pratchett mini-series, the Johnny books, features a character whose name is sometimes Kirsty or Kasandra (depending on her mood) who latches onto a particular cause du jour with all the tenacity of a white shark. Subverted in that Kirsty is anything but meek or flower-child-like; she's dismissive, sarcastic, and ruthlessly efficient.
And another male example in the main Discworld series if Reg Shoe who spends all his spare time going on and on about dead rights. Fortunately this does not irritate his audience too much, as he tends to focus on trying to drum up grass roots support in graveyards, and it has slackened off now he has joined the police force.
Dawn's other defining trait, besides being automatically cool for being from California, was this. Amongst other things, she pretty much started a sermon whenever someone tried to eat meat and tried to get her middle school to change the script of their production of Peter Pan because she thought Wendy's (whom she was playing) role in it was sexist.
In Dawn Saves The Planet, her protesting reaches a point where she runs screaming down the halls at a girl for putting an aluminum can in the trash. That whole book pretty much consists of her doing that to EVERYBODY.
Evelyn in Saki (H. H. Munro)'s "The Forbidden Buzzards" is implied to be this by talking "chiefly about good and evil, and of how much one might accomplish in the way of regenerating the world if one was determined to do one's utmost."
In In the Time of the Butterflies, Minerva Mirabal (a real person) is this. A lot of what she does also counts as Values Dissonance, since the things she wants to do (such as going to college, waiting to get married, and wearing pants) aren't a big deal at all today.
Emma Nelson in the first three seasons is the prime example. She mostly lost this afterwards, though she did climb back on the soapbox every now and then, most notably in the sixth-season episode "Love My Way." Her stepfather Snake, who is also her teacher, catches her buying birth control and gives her a hard time over it. In response, she gives a class presentation over how men are hostile toward female sexuality, which amazingly wins him over instead of making him angry.
Caitlin Ryan, whose character Emma Nelson was very much a successor to. She fought against pollution, animal testing, Spike's expulsion from school because she was pregnant with Emma, and later nuclear missile production (in Canada!).
Also Liz, Spike's best friend, who was the angry Goth version.
At times, Lucy could fit this, though her causes were more focused on feminism and equality.
For one episode of House, Thirteen comes across as this, constantly scoffing at her teammates for not understanding the work of the performance artist whom they are treating. Doesn't really show up otherwise.
The female Mighty Morphin' Power Rangers. It seems almost every episode they were volunteering with kids, cleaning up a park, or participating in some charity. The male Rangers were a Gender Flip of this, but not as extreme. Trini might have been the best example.
Lily Esposito from Popular, especially regarding animal rights/vegetarianism.
Willow edges onto this trope now and then, at the whim of whoever's writing the current episode. The most obvious case was probably in the 4th-season episode "Pangs," in which she rants against the evils of Thanksgiving. In "The Freshman" she says jocularly that she's heard about five different issues and is angry about each and every one of them. In later seasons she also becomes this whenever disparaging stereotypes of witches come up.
Her mother seems to be this in her one appearance on the show where Willow remarks that the longest conversation they ever had was about the supposed patriarchal bias of the Mr Rogers Show.
Carmen Lopez in the two episodes of The George Lopez Show "guest starring" George W. Bush. Thankfully, to tone down the preachy aspect of Soap Box Sadie, she only fits this archetype for those two episodes and it never happens again.
Surprisingly, Doug Heffernan in The King of Queens episode "Offensive Fowl". In this episode, Doug becomes a vegetarian after almost running over a chicken with his truck. Carrie gets tired of having to eat meat in private when he forces his new beliefs onto her. At the episode's end, let's just say thank God for status quo.
Phoebe from Friends slips into this. She vocally criticizes her friends when they do anything that she disapproves of, even when she does them herself.
Rik from The Young Ones is a particularly vicious parody of a male version of this trope; the 'right-on' leftie student activist who, despite coming from an upper-middle class background, has half-read the works of Trotsky and Marx and decided that he represents the working class. Rik is also convinced that he's a ground-breaking poet who, as the 'People's Poet', is an important voice in revolutionary politics and the fight against Margaret Thatcher, and is well-liked and admired by everyone around him. He's wrong on all counts.
Amy Jellicoe from Enlightened definitely qualifies. She is presented compassionately, though. She can be irritating, but she does genuinely care.
New Daily Show correspondent Kristen Schaal seems to have a new cause every time she appears. Due to the show's high cynicism rating, she is also The Woobie as the reality of the situation crushes whatever ideal she starts out with.
A male example can be found in the show Unfabulous in the form of Zach Carter-Schwartz, one of the main character's best friends.
Linda from Round the Twist. At first this was just one facet of her character - later she suffered Flanderization and was turned into an annoying example of the trope while simultaneously losing her judo-fighting badassitude.
Mokey once convinced everyone in Fraggle Rock to stop eating Doozer constructions before learning the hard way that Doozers don't build their constructions for any purpose other than needing to build; without the Fraggles eating them, Doozer buildings began to take over the rock until the Doozers were planning to leave. To really drive the point home, they lamented (within earshot of Mokey, no less) how cruel the Fraggles were to stop eating their towers for absolutely no reason. Hermione Granger definitely should have watched that episode.
Boardwalk Empire has an example less hamfisted than usual in Margaret Schroeder, to the point that it can be considered a subversion. Margaret is an adult woman, and she usually fights against injustices she has genuinely suffered herself: in Season 1 she campaigns for female suffrage, being an immigrant from a country (Ireland) where women can vote to one (America) where they can't; she supports Prohibition because her abusive husband gets even more violent when he drinks, rather than because she thinks that alcohol is intrinsically immoral (and she drinks herself with moderation); and in Season 3 her main struggle is to open a clinic that teaches women to take better care of themselves during pregnancy, having already suffered two miscarriages before 30 herself. The one time she considered fighting for a hopeless cause (bringing Nucky's criminal empire down, which is the basis of her own wealth and status to boot) was when she was stressed and not thinking rationally because of her daughter being sick and blaming herself for it.
On Pramface, Beth harangues both her friends and strangers if they do anything to contradict one of her personal causes, no matter how (sometimes wildly) inappropriate that is.
Lindsay Bluth Fünke from Arrested Development in a subverted version of this trope, often taking up causes whenever they benefit her personally - even when they're contradictory to her actual values. She'll sometimes use these causes to shame her family, but they're quick to point out her hypocrisy.
Michael "The Militant Midget" Evans from Good Times. A spiritual ancestor to The Boondocks' Huey Freeman, he probably would've been a Black Panther, had he been born ten years earlier.
"Prelude/Angry Young Man" by Billy Joel, written from the perspective of an older, more pragmatic ex-activist, gently lampoons this trope:
And there's always a place for the angry young man,
With his fist in the air and his head in the sand
And he's never been able to learn from mistakes,
So he can't understand why his heart always breaks
His honor is pure and his courage as well,
He's fair and he's true and he's boring as hell!
And he'll go to the grave as an angry old man.
Oh, there's always a place for the angry young man
With his working class ties and his radical plans
He refuses to bend, he refuses to crawl,
And he's always at home with his back to the wall
And he's proud of his scars and the battles he's lost,
And he struggles and bleeds as he hangs on his cross
And he likes to be known as the angry young man.
To a point, Alissa White-Gluz of The Agonist. She's a straight-edge vegan animal rights activist who writes songs about humans being bastards who need to show more respect for each other and the environment.
"Fooling Yourself (The Angry Young Man)" by Styx is basically a request for this sort of character to calm down a little. "Why must you be such an angry young man?/Your future looks quite bright to me."
Nemi, from the Norwegian comic strip by the same name. When she's had a bit to drink she turns into a Cloud CuckoolanderGoth. When she hasn't, she is very likely to give you a long Anvilicious speech on everything that is wrong with this world.
Sheila ("I'm very social injustice-conscious") from Hair.
So much so that she leaves him when he becomes absorbed in his own narcissism and stops caring about environmental issues.
Edna Strickland from the 2010 Back to the Future game is an odd deconstruction. In 1931 she's a crusader for moral and social causes, opposing the speakeasy run by Kid Tannen both because of the alcohol and the sultry singer. She even burned down the first speakeasy. Thanks to Marty's alterations to the timeline, Edna falls for a young Doc Brown and, by 1986, she's used his scientific advances to turn Hill Valley into an Orwellian state where "bad behavior" is controlled via brainwashing.
Monique from Sinfest always drifted into this sometimes, but "Trike Girl" lives, breathes, and embodies the trope, always and only. She's also a sort of Author Avatar, so she's always right and never gets the smackdown put on her smug face, making her a bit of a Base Breaker depending on how militant of a feminist you are. Jesus, God, the Devil, and to a lesser extent the Buddha are used as the butt of jokes, but Trike Girl is invariably treated as Serious Business. Not to be outdone, Monique turned the preachinessUp to Eleven at about the same time as Trike Girl first appeared in the comic.
Porrim occasionally drifts this way, but luckily has Kankri's example to warn her off.
Jennie from lonelygirl15, charity worker and feminist. She started to irritate fans during series 3, and the writers attempted to redeem the character by demonstrating that she wasn't all talk. For the most part, this seems to have been successful.
Perkins and Cecil, Chris "Rowdy" Moore's stuffed cats, from TV Trash. If a show has a negative portrayal of cats in ANY way, they will rant about it. In one case, they actually DID done of Moore's reviews for him.
Lisa Simpson of The Simpsons is probably the best-known example, to the point of it turning her into a scrappy in the eyes of certain fans.
In the episode "Bart Star", her soapbox was deflated, as she tried to join the pee-wee football team. "That's right, a girl wants to join the team." After it was revealed that there were four girls already on the team, she tries to raise a fuss about the fact that footballs are made from pigskin. She then learns that the balls are synthetic and with each purchase, money is donated to Amnesty International... She cries when she finds this out. She is later seen reading a book about football injuries.
Her "don't force your beliefs on others" episode was "Lisa the Vegetarian", where she became a vegetarian. She quickly becomes disgusted with everyone else's carnivorous behaviour, culminating in her ruining Homer's big barbecue out of spite. This episode aired in 1995, and she's only gotten worse since then.
The person who approved the episode when the writer proposed it is a vegetarian, and apparently at one time went through the phase Lisa went through in trying to force people, and they decided to make it one of the few developments not subject to a reset button. Mainly because Paul and Linda McCartney were the guest stars, and their sole condition for appearing on the show was that Lisa remain a vegetarian.
As for the in-universe explanation, it is granted that Lisa grew attached to a cutesy baby petting zoo lamb at a storybook village park. You can only guess what they had for dinner that night and how well that went.
The point of that episode was Lisa learning that she shouldn't force other people to become vegetarians, though. She apologizes to Homer at the end.
... which would have been quite touching, had it not played out like this:
Homer: Ohhhh. Lisa. I was looking for you. I wanted to apologize. I don't know exactly what went wrong but it's always my fault.
Granted that Homer was a bit of a Jerkass to her while rousing the family in a catchy conga line tune: "♪You don't win friends with salad♪". It also doesn't help to call your 8-year old daughter a "no-nothing know-it-all".
Particularly amusing was in the episode where she and Burns faced off over a free press and were forced to engage in some small talk:
Burns: So, what do you think of today's popular music scene?
Lisa: I think it distracts people from more important social issues.
Burns: My God, are you always on?
Lisa has also invariably ruined many of Homer's chances at success by insisting that he get on her soapbox, i.e. talk about things that bother/interest Lisa instead of what interests/bothers Homer.
On top of that, she once goaded Marge into disqualifing herself in the final of a cook-off because Marge spiked other entrants' foods with baby medicine, never minding the fact that the other competitors were deliberately sabotaging Marge's hard work in front of her. This wouldn't be so bad, if it wasn't for the fact that the person who'd win was the least-qualified chef in the contest, Brandine Spuckler.
Another episode has the kids go on a field trip to Springfield Glacier, which has been reduced to a tiny hunk of ice in a lake; Lisa spends the entirety of the visit whining about global warming and even demands of her classmates "How can you stand around being kids when serious things are happening?!"
The writers seem to be wary of having Lisa go too far in the direction of this trope, as her political side has been almost completely written out of the show in recent years (or reduced to the occasional one-off gag) in favor of emphasizing her role as the smart-but-isolated middle child, although some recent episodes return to an environmental tract.
A big one is when Lisa protested Christmas by taping the Christmas tree with crime scene tape, on the grounds that they cut down an innocent tree.
One of her worst incidents is in "The Old Man and the Lisa", when she believes that she has turned Burns into an ecologically sensitive businessman. He hasn't of course, but when he fairly offers her final cut of the proceeds, she is so pious that she just... rips up the check dramatically.
Brian from Family Guy has recently mutated into this, delivering liberal and atheist aesops left and right. A few of them made perfect sense (Don't discriminate against gay people) but eventually morphed into such gems as "Religion is for idiots!" and "If we legalized pot everything would be, like, a billion times better!"
Sam Manson from Danny Phantom, pictured above, is an example of the angry Goth; she once put up an entire protest in a single night to counter her best friend's views (though he did the same). In another episode she both complained about people not accepting her for herself andfought to force the whole school to go vegan.
Both of those things happened in the same episode- Tucker's protest was in response to Sam forcing the whole school to go vegan, and Sam's counter-protest was a response to Tucker's protest.
Ophelia on The Life and Times of Juniper Lee is a comic example of the angry Goth. When June wants to keep people out of a particular forest, she simply makes up a new endangered species that lives there, and Ophelia, like a flash, is barricading the forest off.
The title character of Daria is an exception: While she is very self-righteous about her chosen causes, and often wonders whether she's forcing her beliefs on others, the fact that she doesn't seem to care much whether she actually has any influence on others means she does not fit the standard two types very well. This gradually subverted in the last season episode "Fizz Ed," when she is convinced she has to personally take action against the school's soda pop contracting and succeeds in reining it back.
Worth noting that even when she did take action in "Fizz Ed", Daria didn't actually get the results she was after. It took the school's principal suffering a Freakout brought on by stress and high amounts of caffine, followed by district's superintendent walking in and witnessing the proverbial carnage. It's actually noted at the end of the episode that the scaling-back of the contract couldn't be traced to her.
Also, Daria was not exactly willing to confront Ms. Li or the superintendent on the matter because she doesn't "get involved" until Jodie and Tom told her she only has the right to complain if she's willing to do something about it.
A straighter example of this trope would be Jane's older sister Penny, who backpacks in third world countries while attempting to sell handmade knickknacks as a way to salvage the economies. However, Penny clearly has little understanding in terms of foreign languages and the countries she's trying to "save".
Subverted two ways by Bobby Hill from King of the Hill. The first being that he's a boy, the second being -more importantly- that while he frequently invests himself in various social causes, he's more like a real adolescent in his approach: very self-righteous and emotional, but also very ill-informed and myopic; usually just buying right into whatever his teachers or peers tell him without thinking it through.
Joseph: Did you ask her out yet? Bobby: I tried to, but she's too busy trying to save the world.
Another episode has him fall sway to a fire and brimstone style preacher which leads him to stand in the mall calling everyone around him a fornicator. His highest point of religious zeal is destroying his dads papier mache statue of Uncle Sam because Hank was worshiping "false idols".
On the other hand, this was nicely subverted in one of the later episodes of the series where he goes through a green-phase due to a movement at school. Hank thinks it's stupid at first, but soon learns much of it is common sense and small, reasonable sacrifices. It's shown that many other people in the green movement (who fit more into the usual Soapbox Sadies) are only in it because it's "hip" though, including Hank's boss, who only does it to bed women. After Bobby grows disillusioned with so many people being interested in going green because it's a fad, Hank ends the episode by helping him plant a tree in their yard and telling him he's doing something good and not to let the people who're only on the bandwagon get to him.
In "Imprisoned", she let herself be captured by the enemy to infiltrate and liberate a rig of Earthbenders.
In "The Painted Lady", she faked Appa's illness to stay and have more time in a village to help their sick people, putting on hold the team mission.
In "The Waterbending Master", she confronted the traditions of a culture to gain the right to learn combative waterbending, which was forbidden to the women of the tribe (and, by extension, to her).
Of course, in "The Ember Island Players", the woman who plays Katara in the play about the Avatar's journey is a very over-the-top, swooning, love-and-friendship preaching mess. Katara tries to deny that she is anything like that in real life, earning an awkward "uh, yeah you are" from her friends. Though she does have her moments of badass straightforwardness, in general Katara is (sometimes blindly) idealistic.
Stan: I hate the last day of camp. You better write me when you get home.
Hot Rod: We do not have homes. The rebels destroyed them all.
Stan: Oh yeah. Guess I don't like thinking about the horrible situation you people live in.
Kid sets a literal soapbox in front of him, Stan steps onto it, looking straight at the camera*
Stan: Just like the rest of the world. Shame on you!
While Hayley is strongly against her father's views on how wives (and women in general) should be treated or act, one episode revealed Hayley in an outfit and hairstyle from the 1950s while baking pie. Francine discovers this and humorously points out the hypocrisy in it all.
Technically, it's not hypocrisy if acting that way is solely the woman's choice. It's only bad if someone who isn't a woman forces women to act that way.
Alyssa from My Dad The Rock Star fits the trope in that she campaigns for nature and individuality, but mostly not to an obnoxious level.
Done by Jenny in My Life as a Teenage Robot in a one-off episode involving "Wiggly World", where robots were "slaves" by her estimation. She frees them to disastrous results - including one blowing up because it couldn't do its job.
Courtney from Total Drama Island qualifies: she does genuinely try to be a polite girl, and thanks to some character development in the first half of season 3 she does come across as genuinely nice at times. At the same time, she's overly preachy, blindly follows the rules, and tends to be rather condescending; Duncan also shows her that being evil is also kind of fun. Hell she's even written a BOOK SERIES on how to be a successful teen.
In the My Little Pony: Friendship Is Magic episode "Feeling Pinkie Keen", Pinkie Pie has an ability to predict the future that Twilight Sparkle can't seem to explain rationally. When Pinkie asks what the difference is between her ability and Twilight's magic, Twilight stands on a literal soapbox and lectures Pinkie on how magic is practiced and codified, while her "Pinkie Sense" is random and unexplainable. However, by the end of the episode, Twilight learns that just because you can't explain something doesn't mean it's not real, as she's forced by experience to concede that Pinkie's powers are real.
It doesn't look like the lesson stuck.
There were shades of this in Bats! between Fluttershy and Applejack, with Fluttershy trying to stand up for the fruit bats even though they were destroying Applejack's crops. The real lesson was about not forcing your friends into doing something they don't think is right (Applejack and the others badgering Fluttershy into helping them mess with the bats) but they end up having Fluttershy be right about the bats behaving after Applejack lets them have a section of the orchard to themselves even though there was no indication this would work earlier on and invasive species are an actual problem.
Miss Grotke from Recess can be this in her lessons at times, and a rare example of not being a teenager/child, as she's roughly in her thirties somewhere.
Jean from X-Men: Evolution could tip into this, what with her speeches on mutant pride and mutant/human equality. It was even lampshaded at one point, in which she gears herself up for a lecture: "And I for one, am very proud of the fact..." only to be yanked off-screen by Scott.
In the Girls Night Out episode she and the other mutant girls rail against Scott's overprotectiveness and start fighting crime as the "Bayville Sirens." She mellows out by the end of the episode.
Wendy Testaburger from South Park. Sometimes Played for Laughs (unsurprising, given the nature of the show) but there have been frequent moments where Matt & Trey have used her for delivering legitimate liberal Aesops and Author Tracts.