Bad Export for You: The European console versions were censored, though the PC version was uncut. Though the "bad export" part is debated since among the things which were removed for censorship were a series of minigames which were generally hated due to bugs or annoyingly precise input requirements.
Development Hell: The game was supposed to be released in late 2012 before being delayed. Twice. Then it was delayed again, and its release date was eventually in 2014. This was almost entirely due to Parker and Stone constantly rewriting the script. The season 17 episode "Black Friday" had Cartman raging about the worthlessness of pre-orders for video games, and sarcasm around the game "coming soon."
One of Us: Parker and Stone filled the game's script with parodies, deconstructions, and references to various RPGs and tropes.
Pre-Order Bonus: Those who preordered the game received a few extra outfits.
Release Date Change: Originally set for release in 2012, but got delayed to April 2013 considering the financial difficulties of THQ. When the publisher went bankrupt and the asset sold to Ubisoft, the release date was moved even further to December 11, 2013, then March 4, 2014. It's become so infamous that the show itself has referenced it. To paraphrase Cartman, dressed in his Stick of Truth outfit: "You know what you get when you reserve a game? A big dick in your mouth!"
Voiceover at the end of Titties and Dragons: The South Park video game, coming to stores soon!
Butters: Yeah, and if you believe that, I've got a big floppy weiner to dangle in your face.
At San Diego Comic-Con 2013, Trey Parker revealed that the original script for the game was approximately 850 pages long. He was urged to trim the script, though he felt that eventually some of the discarded ideas could be used in the actual show. At one point, he'd thought of incorporating the game into the next season, but figured it would be more accessible as a standalone project. Though the Black Friday / Game of Thrones trilogy in season 17 (which includes promotions for the game) was probably the result of these plans.
The original Game Informer magazine cover and article suggested a wholly different game, most obviously showing an alternate, unused costume design for Kenny as a princess◊. Instead of wearing the purple Zelda-esque dress, he was to wear an orange dress and would not wear his parka underneath, allowing his face to be exposed. Due to the exposure of his face, he was also shown to be wearing makeup. This was most likely scrapped because it made him unrecognizable and too much like an actual female, due to the show's art style.
The same cover shows other characters and elements for the game that were scrapped, such as Satan, and just about every minor character (save Scott Malkinson) has a completely different outfit than in the final game.
The girls were to have a bit more of a role, with New Kid and his friends having to fight schoolyard hookers in some boss battles. A "Cheerleaders vs. Whores" fight was also visible in trailers and early gameplay footage.
Clyde was also to be another final boss (as seen in the early trailer), while the Vampire Kids, Ginger Kids, and Hippies were other types of enemies that were excluded.
The Woodland Critters and Crab People were to be battle bosses and summons, but were cut through production of the game.
There were to be more Facebook friends for New Kid to add, one of them being Kenny's former girlfriend Kelly from "Rainforest Schmainforest". Kelly alludes to being "emotionally damaged" and requests that the player be Facebook friends with her rather than make her commit to an actual relationship. A few of these other characters do appear in the game, but cannot be added as a friend, like Monica's boyfriend Jake and Enchorito Mark.
Under THQ, the game was going to have several European language dubs, using the show's respective voice cast in each language - dubbed trailers were even made. When the assets were sold to Ubisoft, the dubs were scrapped, and each country only got translated text with English voices. Ironically, Ubisoft is based in France, where dubbing is almost always favored.
Pharaocious, a Chinpokomon Captain Ersatz of Lucario, was planned for the game, but ultimately scrapped. It can still be seen as one of the Chinpokomon shown on the achievement icon for collecting all Chinpokomon.
A few people have acquired the THQ build under orders not to distribute it. Videos from these builds show multiple additional characters and locations as part of the original Goth Kids' questline. While recruiting the Goth Kids as in the final game, the player is tasked with defeating Vampire Kids in the cemetery behind the Church, where they are using the (seemingly abandoned) South Park Genetic Engineering Ranch to try to summon H. P. Lovecraft to defeat otherwordly beings. After a boss battle with Mike "Vampir" Mc Kowski, their leader, the player meets the Goth Kids at Perkins' restaurant (previously a Village Inn or Benny's in the show, depending on the episode) and they summon Lovecraft (and briefly Michael Jackson) only to be disappointed in him. A potential truce at Vampir's House (locked in the final game) results in the discovery the beings are, in fact, Crab People.
The game's files still yet included just a few small files for EV Games and Hell's Pass Hospital (nothing compared to the final locations) and there's also two lines for Dr. Doctor/Dr. Gouache ("This colon's gone spastic!") but there's no indication how he might've fit into the game.
The files relating to the 'Inn of the Giggling Donkey' level, which Ubisoft trailers and the final game indicate takes place at the Valmer Residence, and sets up the boss battle with Jimmy, all refer to it as the Donnely House, referring to Canon Foreigner Chris Donnely, who also has extra boss dialogue in the files. Like everything else, this seems to have been a casualty of moving to Ubisoft.