Question: Which season of American Idol did the California Gurls artist guest judge?

full_context: Document 1: This Is How We Do: "This Is How We Do" is a song recorded by American singer Katy Perry for her fourth studio album, "Prism" (2013). Perry co-wrote the song with its producers Max Martin and Klas Åhlund and recorded it in Stockholm, Sweden. The song was released as the album's fifth and final single on August 11, 2014. "This Is How We Do" is a dance-pop song influenced by hip hop, having "synth squiggles" and "melodic dots" as its main instrumentation. Lyrically, it has Perry sing-talking about her hangout routine with her friends. The song's official remix featuring American rapper Riff Raff was released on August 25, 2014.
Document 2: Part of Me (Katy Perry song): "Part of Me" is a song by American singer Katy Perry, released as the lead single from "". It was written by Perry, and Bonnie McKee, with production and additional writing by Dr. Luke, Max Martin, and Cirkut. The song was not included on the original edition of "Teenage Dream" because Perry felt that it did not fit the composition of the album. A demo of the song leaked online in late 2010, amid speculation that the lyrics were directed to the singer's ex-boyfriend Travie McCoy. "Part of Me" was re-worked and officially released on February 13, 2012, through Capitol Records with artwork by art director Gavin Taylor and photography by Mary Ellen Matthews.
Document 3: American Idol: In season eight, Latin Grammy Award-nominated singer–songwriter and record producer Kara DioGuardi was added as a fourth judge. She stayed for two seasons and left the show before season ten. Paula Abdul left the show before season nine after failing to agree terms with the show producers. Emmy Award-winning talk show host Ellen DeGeneres replaced Paula Abdul for that season, but left after just one season. On January 11, 2010, Simon Cowell announced that he was leaving the show to pursue introducing the American version of his show The X Factor to the USA for 2011. Jennifer Lopez and Steven Tyler joined the judging panel in season ten, but both left after two seasons. They were replaced by three new judges, Mariah Carey, Nicki Minaj and Keith Urban, who joined Randy Jackson in season 12. However both Carey and Minaj left after one season, and Randy Jackson also announced that he would depart the show after twelve seasons as a judge but would return as a mentor. Urban is the only judge from season 12 to return in season 13. He was joined by previous judge Jennifer Lopez and former mentor Harry Connick, Jr.. Lopez, Urban and Connick, Jr. all returned as judges for the show's fourteenth and fifteenth seasons.
Document 4: American Idol: With the exception of seasons one and two, the contestants in the semifinals onwards perform in front of a studio audience. They perform with a full band in the finals. From season four to season nine, the American Idol band was led by Rickey Minor; from season ten onwards, Ray Chew. Assistance may also be given by vocal coaches and song arrangers, such as Michael Orland and Debra Byrd to contestants behind the scene. Starting with season seven, contestants may perform with a musical instrument from the Hollywood rounds onwards. In the first nine seasons, performances were usually aired live on Tuesday nights, followed by the results shows on Wednesdays in the United States and Canada, but moved to Wednesdays and Thursdays in season ten.
Document 5: American Idol: The fourteenth season premiered on January 7, 2015. Ryan Seacrest returned to host, while Jennifer Lopez, Keith Urban and Harry Connick, Jr. returned for their respective fourth, third and second seasons as judges. Eighth season runner-up Adam Lambert filled in for Urban during the New York City auditions. Randy Jackson did not return as the in-house mentor for this season.
Document 6: American Idol: The show had originally planned on having four judges following the Pop Idol format; however, only three judges had been found by the time of the audition round in the first season, namely Randy Jackson, Paula Abdul and Simon Cowell. A fourth judge, radio DJ Stryker, was originally chosen but he dropped out citing "image concerns". In the second season, New York radio personality Angie Martinez had been hired as a fourth judge but withdrew only after a few days of auditions due to not being comfortable with giving out criticism. The show decided to continue with the three judges format until season eight. All three original judges stayed on the judging panel for eight seasons.
Document 7: Peacock (song): "Peacock" is a song by American singer Katy Perry, taken from her third studio album, "Teenage Dream" (2010). Because the song was filled with suggestive lyrics pertaining to male genitalia, Capitol Records initially opposed the idea of including it on her record. Similar to what happened with another song of hers – "I Kissed a Girl" (2008) – she refused to withdraw it from the record. "Peacock" was panned by music critics and, musically, was compared to the 1980s hit "Mickey" by Toni Basil, and Gwen Stefani's "Hollaback Girl" (2005). On March 26, 2012, a remix version was released as promotional single on iTunes.
Document 8: American Idol: American Idol employs a panel of judges who critique the contestants' performances. The original judges were record producer and music manager Randy Jackson, pop singer and choreographer Paula Abdul and music executive and manager Simon Cowell. The judging panel for the most recent season consisted of country singer Keith Urban, singer and actress Jennifer Lopez, and jazz singer Harry Connick, Jr. The show was originally hosted by radio personality Ryan Seacrest and comedian Brian Dunkleman, with Seacrest continuing on for the rest of the seasons.
Document 9: The One That Got Away (Katy Perry song): "The One That Got Away" is a song by American singer Katy Perry for her third studio album, "Teenage Dream" (2010). The song was produced by Dr. Luke and Max Martin, both of whom also co-wrote the song with Perry. The song is a mid-tempo pop ballad about a lost love. It features references to the rock band Radiohead as well as the relationship of Johnny Cash and June Carter Cash to express the strength of the relationship. The song was released in October 2011 by Capitol Records as the album's sixth single.
Document 10: California Gurls: "California Gurls" is a song recorded by American singer Katy Perry. It served as the lead single for her third studio album, "Teenage Dream" (2010). The song features verses from rapper Snoop Dogg. Both artists co-wrote the song with Bonnie McKee and its co-producers Dr. Luke and Max Martin, with additional production from Benny Blanco. According to Perry, "California Gurls" is an answer song to "Empire State of Mind" (2009), by Jay-Z and Alicia Keys. Its midtempo production incorporates disco-pop and funk-pop with influences of new wave and electropop. Its lyrics are an ode to the state of California, in which both Perry and Snoop Dogg were born and raised.
Document 11: Dressin' Up: "Dressin' Up" is a song by American singer Katy Perry from "" (2012). It was written by Perry, Christopher "Tricky" Stewart, Monte Neuble, and Matt Thiessen, and produced by Stewart and Kuk Harrell. Musically, "Dressin' Up" incorporates the styles of electro and dance-rock, along with a prominent electronic dance production. Lyrically, the song speaks of dressing up in different outfits for a lover, and contains multiple innuendos. "Dressin' Up" garnered mixed reviews from critics, some of whom complimented its "fun" sound, while others denounced it as being too similar to Perry's other works. Upon the release of "Teenage Dream: The Complete Confection", the song charted on the UK Singles Chart at number 109.
Document 12: American Idol: Guest judges may occasionally be introduced. In season two, guest judges such as Lionel Richie and Robin Gibb were used, and in season three Donna Summer, Quentin Tarantino and some of the mentors also joined as judges to critique the performances in the final rounds. Guest judges were used in the audition rounds for seasons four, six, nine, and fourteen such as Gene Simmons and LL Cool J in season four, Jewel and Olivia Newton-John in season six, Shania Twain in season eight, Neil Patrick Harris, Avril Lavigne and Katy Perry in season nine, and season eight runner-up, Adam Lambert, in season fourteen.
Document 13: I Kissed a Girl: ``I Kissed a Girl ''is a song recorded by American singer Katy Perry for her second studio album, One of the Boys (2008). It was released on April 28, 2008, by Capitol Records as the lead single from the record. Perry co-wrote the song with its producers Dr. Luke and Benny Blanco, with additional songwriting provided by Max Martin and Cathy Dennis.`` I Kissed a Girl'' is a pop rock song with elements of new wave. Perry stated its lyrics are ``about the magical beauty of a woman ''. The song sparked controversy for its homosexual themes.
Document 14: American Idol: Beginning in the tenth season[citation needed], permanent mentors were brought in during the live shows to help guide the contestants with their song choice and performance. Jimmy Iovine was the mentor in the tenth through twelfth seasons, former judge Randy Jackson was the mentor for the thirteenth season and Scott Borchetta was the mentor for the fourteenth and fifteenth season. The mentors regularly bring in guest mentors to aid them, including Akon, Alicia Keys, Lady Gaga, and current judge Harry Connick, Jr..
Document 15: I Kissed a Girl: ``I Kissed a Girl ''is a song recorded by American singer Katy Perry for her second studio album, One of the Boys (2008). It was released on April 28, 2008, by Capitol Records as the lead single from the record. Perry co-wrote the song with Max Martin, Cathy Dennis, and its producer Dr. Luke, with additional production from Benny Blanco.`` I Kissed a Girl'' is a pop rock song with elements of new wave. Perry stated its lyrics are ``about the magical beauty of a woman ''. The song sparked controversy for its homosexual themes.
ground_truth: season nine
sub_queries: California Gurls >> performer Answer: Katy Perry
Which season of American Idol featured Katy Perry as a guest judge? Answer: season nine