South Park: The Fractured But Whole doesn't release until tomorrow, but you can start preparing for it right now. Below, you will find a collection of episodes worth watching before embarking on The New Kid's latest adventure. These particular episodes will serve as refreshers for some of the characters and assorted referential jokes featured prominently in the game.
Season 6, Episode 6: “Professor Chaos”
Butters and his Professor Chaos persona are a big part of The Fractured But Whole. This is the episode where Butters invented the alter ego.
Season 7, Episode 5: "Fat Butt and Pancake Head"
A South Park character we haven't heard much from lately is introduced here. It would be good to remember who they are.
Season 12, Episode 3: "Major Boobage"
This episode introduces the concept of "cheesing," which is something the children encounter in The Fractured But Whole.
Season 12, Episode 13: "Elementary School Musical"
This episode is notable for introducing a relatively minor character named Scott Malkinson. Malkinson and his superhero alter ego, Captain Diabetes, play a much larger role in the game.
Season 13, Episode 5: “Fishsticks”
Kanye West appears in this episode, getting increasingly frustrated by a joke he does not understand. Trey Parker teased West’s inclusion on stage at E3 2016, so it would be a good idea to remember how he made his way into South Park lore.
Season 13, Episode 2: “The Coon”
This is the episode where Cartman's alter ego, The Coon, is introduced, along with Mysterion. The episode serves as a spoof of many of the popular superhero films of the time, like Watchmen and The Dark Knight.
Season 14, Episodes 11, 12, & 13: "Coon 2: Hindsight", "Mysterion Rises", and "Coon vs. Coon and Friends"
Season 14’s three-part run has the most direct line to Fractured, as it introduces nearly all of the hero alter egos that appear in the game. It outlines everyone’s abilities, including which kids have real powers and which ones are only pretending.
Season 15, Episode 14: "The Poor Kid"
Though not a mainline Coon episode, “The Poor Kid” features Mysterion (Kenny’s alter-ego) as he confronts his family’s poverty and helps his younger sister.
Season 19, Episode 1: "Stunning and Brave"
PC Principal is introduced in this episode, who plays a small role in Fractured But Whole.
Season 19, Episode 6: "Tweek x Craig"
“Tweek x Craig” explores yaoi, the Japanese art form focused exclusively on romantic relationships between male characters. In the episode, Tweek and Craig become unwilling subjects of yaoi art, and that forced relationship extends into Fractured.
Season 19, Episode 10: "PC Principal Final Justice"
Classi and the strange way in which she spells her name is introduced here. She makes an appearance in Fractured.
Season 20, Episode 1: "Member Berries"
Remember this episode? It was a good one.
Season 21, Episode 4: "Franchise Prequel"
As the name implies, this episode serves as a prequel of sorts for the game. It ultimately doesn't make canonical sense considering Stick of Truth is supposed to take place right before the game, but canon has always been fluid in South Park.
Source : http://www.gameinformer.com/b/features/archive/2017/10/16/15-episodes-of-south-park-to-watch-before-playing-the-fractured-but-whole.aspx