Keith Urban will appear in a Gap ad campaign this fall, wearing jeans and performing a cover of Billy Thorpe's "Most People I Know Think I'm Crazy." Urban's version of the song is also included on a compilation CD to be sold at the Gap. The campaign "focuses on how jeans and songs are individual expressions of personality and style," according to a press release. Other participating artists include Alanis Morissette, Jason Mraz, Liz Phair, Joss Stone and Michelle Williams. Customers who try on a pair of jeans between Aug. 8 and Aug. 31 in the store will also receive an iTunes gift certificate for a free download.