Singer Frank Ocean is facing a lawsuit after allegedly backing out of a deal to record a song for an advert by a fast food chain. The star was reportedly hired to sing a cover version of Pure Imagination from 1971 movie Willy Wonka & the Chocolate Factory for an animated TV commercial by U.S. restaurant chain Chipotle Mexican Grill. However, bosses at the company have now filed a lawsuit accusing Ocean of backing out of the deal following a dispute over the use of the firm's logo in the TV spot. In the lawsuit filed at a court in Los Angeles County on Friday (07Mar14), and obtained by TMZ,com, Chipotle Mexican Grill bosses demand the return of the $212,500 (£132,813) advance allegedly paid to Ocean for the work. The song for the advert was recorded by singer/songwriter Fiona Apple after Ocean exited the project.