I dedicate a short novel to how much South Park.changed for me. I wrote about the stages, the most important changes and what was typical of that era:
1-3 season: The initial era
The series at the beginning contained fairy tale elements.
Fairytale elements: Officer Barbrady's thought bubble in "Weight Gain 4000" and in "Chickenlover", the fight with Mecha Streisand, Stan's fish from an evil parallel universe kills people, Mr. Mackey's head floating due to LSD and the boys can see it, the probability of spontaneous combustion, the characters' interaction with the narrator.
Fictional characters: Scuzzlebutt, Mr. Hankey, Big Black Scary Monster Underpants Gnomes, Jakovasaurs.
In this era Cartman's personality was the best in the whole series. Think about his catchphrases: "Respect my authoritah!", "Screw you guys, I’m going home!", “That’s a bad Mr. Kitty!”, “I’m not fat, I’m big boned!”.
The boys didn't know the meaning of lesbian and where are babies come from.
Parents didn't let their children watch the Terrance and Phillip show because of its language and farts.
Liane was portrayed as a "she sleeps with everyone" slut.
Mr. Garrison had Mr. Hat on his hand and used it as evasion like in "Weight Gain 4000".
The legendary returning-gag when Kenny dies in almost every episode.
Stan or Kyle said this in every episode's end: “You know, I learned something today,”.
Shelly was so unlikeable and beat the crap out of Stan.
When Comedy Central didn't like things that wouldn't be imaginable today. E.g.: Comedy Central executives didn't think Cartman's Hitler costume was a good idea, so they suggested other ideas, but Parker and Stone insisted on Hitler's costume. When an episode title is not allowed to include the word "fuck". When a 2,000 email was written by outraged fans over an episode.
The well received movie was released after "Tweek vs. Craig".
The episodes in this era were no better than the following season's episodes.
4-6 season: The alteration era
There are still fairy tale elements but not as many as in the previous era.
This era is a transition from fabulous elements to a more realistic representation.
Fairytale elements: Tuong Lu Kim's wall was attacked by native Mongolians, Chef’s TV broke loose in town and started shooting, the butthead couple, the character Towelie, Cartman's trapper keeper turned into a monster, time travel in "Fourth Grade".
The boys were disillusioned with the existence of the tooth fairy.
Dr. Mephesto was no longer found to be funny, so in "Cartman Joins NAMBLA" he was written out of the series. Only a few cameo appearances until 201.
From season 5 the animation was made by Maya instead of PowerAnimator.
From the episode "Fourth Grade", to "Kenny Dies", a hip-hop version of the song was used, which was remixed by Paul Robb. The intro with the band's lead singer is not used anymore.
Timmy, the appearance of a mentally handicapped character on screen was preceded by great controversy with Comedy Central.
Episode "Quintuplets 2000" is a milestone. It was the first time when Trey and Matt took advantage of the short production time and reacted to a current event within the framework of the series.
Mohamed was able to appear without a hitch in the episode "Super Best Friends'' and in the opening scenes thereafter.
The children still do not understand some mature things. In "Proper Condom Use," sexual education classes are being introduced at South Park Elementary School, however, teachers' unpreparedness is causing serious problems among students. In "The Return of the Fellowship of the Ring to the Two Towers" the parents explain some mature things about the content of the sex video to their children.
In "Kenny dies" Trey and Matt finally killed Kenny and until "Red Sleigh Down" he was absent.
In season 6 Butters becomes a major character, he is best known for his unusual good nature.
7-10 season: The Peak era
In this era, they are only showing unlikely things that have a chance to happen but will not happen in real life e.g.: Painted on Cartman's palm Jennifer Lopez infuriates the real Jennifer Lopez, Native Americans want to grab South Park for themselves to build a highway, the water flood the adjacent town of Beaverton.
Detective Harrison Yates became a more major character and slowly replaced Officer Barbrady.
Chef barely appeared and died in "The Return of Chef".
Chef's voice actor Isaac Hayes, announced that he was leaving the series because of the episode: Trapped in the Closet.
Hereupon Kenny only dies in a few episodes. First in "It's Christmas in Canada".
Mr. Hankey doesn't come up from the toilet anymore and won't have a role until 201.
This era contains Cartman's best moments in the following episodes: Casa Bonita, Toilet Paper, I'm a Little Bit Country, Fat Butt and Pancake Head, AWESOM-O, The Death of Eric Cartman, Tsst.
There are still Comedy Central interventions e.g. in "Mr. Garrison's Fancy New Vagina".
In a two-part episode called Cartoon War, Comedy Central didn't allow the creators to actually portray Mohamed in the episode.
11-15 season: The post-peak era
There have been celebrities before, but far from as many as in the upcoming episodes. More and more episodes came out where celebrity characters have major roles: Tonsil Trouble, Britney's New Look, Fishsticks, Dead Celebrities, 200, 201.
In "200" Muhammad reappeared censored again, in 201 the Comedy Central censored all visual or aural references to Mohamed because of Muslim threats. Kyle's speech at the end of the episode was censored that had nothing to do with Muhammad.
"200" and "201" contain many returning jokes and characters who have not been featured for years or only rarely. E. g.: Mr. Hankey, Mr. Hat, Mecha-Streisand, Hennier Lopez, Santa, Officer Barbrady, Dr. Alphonse Mephesto.
16-18 season: The beginning of declining era
The low point of the series (I think) is season 16 where almost the worst episodes were made: A Scause For Applause, Jewpacabra, I Should Have Never Gone Ziplining.
The episode "Goth Kids 3: Dawn of the Posers" missed its deadline due to power outage. This was the first time the creators couldn't keep the deadline.
Best trilogy since the series came into existence: Black Friday Trilogy.
In season 18 there are references to previous episodes in this season but it does not form a complete story.
In #REHASH we saw the iconic Bus Stop and it wasn't used until Moss Piglets, almost 3 years later.
19-23 season: The reinvent era
To keep the series fresh, episodes are created to react to an event, ignoring character development.
Many times I feel that Trey and Matt are taking advantage of the characters to endow them with traits that are then later forgotten. E.g.: Randy and Sharon started a television series titled White People Renovating Houses, Randy became a PC member, Gerald trolled the internet as Skankhunt42. With many characters they seem to not know what to do.
The city people have a more major role, they react to events or trends.
In the 19. season, they came up with the idea that to do serialized storylines throughout the season.
Season 20: they came up with a season long plot with many plot holes, they were forced to re-write "The Very First Gentleman" episode.
The first special: The Pandemic Special. They made the best episode reacting to the current events (COVID-19, police abuses) This special is better than all of the episodes in this era.
For me, South Park still means there are four swearing guys: Cartman, Kyle, Stan and Kenny. I prefer to look at children’s problems rather than adults'.
I’d rather look back on older episodes, especially around 7-10 seasons.