announced that he would release two songs on the soundtrack for the film Cars 2. One of them would be a collaboration with British pop singer Robbie Williams. On September 21, 2011, Mailboat Records released Mark Twain: Words & Music, a double-CD telling Mark Twain's life in spoken word and song, including a new song by Paisley titled "Huck Finn Blues". Paisley's website announced that he was a fan of Twain, prompting his collaboration on the project with Clint Eastwood, Jimmy Buffett, Sheryl Crow, Vince Gill, and others. On October 19, 2011, Paisley made a voice cameo as various background characters in the South Park episode "Bass to Mouth". On January 14, 2012, Paisley was a guest on Garrison Keillor's Prairie Home Companion, during which he did a rendition of "Life's Railway to Heaven" by Charles Davis Tillman. On April 25, 2012, Paisley was featured on the South Park episode "Cartman Finds Love", in which he voiced himself, sang the national anthem and helped Cartman sing the 1990s hit song "I Swear", which was popularized in 1994 by the country musician John Michael Montgomery and the pop group All-4-One. Paisley extended his Virtual Reality World Tour through mid-2012. He toured the country and made pit stops at local country music festivals. 2012–2014: Wheelhouse On September 20, 2012, Paisley released a new single, "Southern Comfort Zone". The song debuted at number 25 on the Hot Country Songs chart, becoming Paisley's highest debut to date. It reached number 2 on the Country Airplay chart in 2013. The song was the first single from his ninth studio album, Wheelhouse, released on April 9, 2013. The album's second single, "Beat This Summer", was released to country radio on March 4, 2013. It also reached number 2 on the Country Airplay chart in July 2013. The album's third single, "I Can't Change the World", was released to country radio on August 19, 2013: despite a moderately good debut, the single failed to reach the top 20 on country charts, peaking at number 22 on Country Airplay and becoming Paisley's lowest-charting single to date. The album's fourth single, "The Mona Lisa", was released to country radio on December 9, 2013. It peaked at number 19 on Country Airplay. On June 12, 2013, Paisley announced on his Twitter page that he would join the Rolling Stones onstage during the band's concert in Philadelphia. His track "Accidental Racist",