The group released its fourth album, "Mmhmm", in late 2004. Pop-culture references were even less specific than on the band's third album, if present at all. The album was significantly more on the serious side with very few of the silly songs the band was known for. The album had the band experimenting with its sound a bit more, which included incorporating piano, hardcore punk and some pop music. In July 2005, the album was certified gold for shipping over 500,000 copies. It is reported that it has sold approximately 796,000 copies. Driven by newfound recognition from "Mmhmm", "Two Lefts Don't Make a Right...but Three Do" was also certified gold in spring 2005. Also, it was announced in 2006 that the band's second record, "The Anatomy of the Tongue in Cheek", had reached the Gold rank as well as certified by the RIAA.