The Grey Album, a mashup of Jay-Z's Black Album and The Beatles' White Album, was a breakthrough for Danger Mouse and a controversial release due to copyright issues. Despite legal action from EMI, the album gained attention and was downloaded over 100,000 times in 24 hours after being released for free by the organization Downhill Battle. The situation led to minimal legal consequences for those involved and helped launch Danger Mouse's career, leading to his work on Gorillaz's Demon Days album.