Parker and Stone signed a deal with Comedy Central in April 1998 that contracted the duo to producing South Park episodes until 1999, gave them a slice of the lucrative spinoff merchandising the show generated within its first year, as well as an unspecified seven-figure cash bonus to bring the show to the big screen, in theaters. During the time, the team was also busy writing the second and third seasons of the series, the former of which Parker and Stone later described as "disastrous". As such, they figured the phenomenon would be over soon, and they decided to write a personal, fully committed musical. Parker and Stone fought with the MPAA to keep the film R-rated; for months the ratings board insisted on the more prohibitive NC-17. The film was only certified an R rating two weeks prior to its release, following contentious conversations between Parker/Stone, Rudin, and Paramount Pictures. Parker felt very overwhelmed and overworked during the production process of the film, especially between April and the film's opening in late June. He admitted that press coverage, which proclaimed the end of South Park was near, bothered him. South Park: Bigger, Longer & Uncut opened in cinemas in June 1999 and received critical acclaim while grossing $83 million at the box office.
South Park has continued, becoming an enterprise worth hundreds of millions of dollars. The franchise has also expanded to music and video games. Comedy Central released various albums, including Chef Aid: The South Park Album and Mr. Hankey's Christmas Classics, in the late 1990s. The song "Chocolate Salty Balls" (as sung by the character Chef) was released as a single in the UK in 1998 to support the Chef Aid: The South Park Album and became a number one hit. Parker and Stone had little to do with the development of video games based on the series that were released at this time, but took full creative control of South Park: The Stick of Truth, a 2014 video game based on the series that received positive reviews and for which they shared (with Eric Fenstermaker) the 2014 Writing In A Comedy and Parker won the Performance in a Comedy, Supporting award by National Academy of Video Game Trade Reviewers (NAVGTR). Broadcast syndication rights to South Park were sold in 2003, and all episodes are available for free full-length on-demand legal streaming on the official South Park Studios website. In 2007, the duo, with the help of their lawyer, Kevin Morris, cut a 50-50 joint venture with Comedy Central on all revenue not related to television; this includes digital rights to South Park, as well as films, soundtracks, T-shirts and other merchandise, in a deal worth $75 million.