<P> David Saltzberg, a professor of physics and astronomy at the University of California, Los Angeles, checks scripts and provides dialogue, mathematics equations, and diagrams used as props . According to executive producer / co-creator Bill Prady, "We're working on giving Sheldon an actual problem that he's going to be working on throughout the (first) season so there's actual progress to the boards...We worked hard to get all the science right ." </P> <P> Several of the actors in The Big Bang Theory previously worked together on the sitcom Roseanne, including Johnny Galecki, Sara Gilbert, Laurie Metcalf (who plays Sheldon's mother, Mary Cooper), and Meagen Fay (who plays Bernadette's mother). Additionally, Lorre was a writer on the series for several seasons . </P> <P> The Canadian alternative rock band Barenaked Ladies wrote and recorded the show's theme song, which describes the history and formation of the universe and the Earth . Co-lead singer Ed Robertson was asked by Lorre and Prady to write a theme song for the show after the producers attended one of the band's concerts in Los Angeles . By coincidence, Robertson had recently read Simon Singh's book Big Bang, and at the concert improvised a freestyle rap about the origins of the universe . Lorre and Prady phoned him shortly thereafter and asked him to write the theme song . Having been asked to write songs for other films and shows, but ending up being rejected because of producer's favor of other artist's song, Robertson agreed to write the theme only after learning that Lorre and Prady had not asked anyone else . </P> <P> On October 9, 2007, a full - length (1 minute and 45 seconds) version of the song was released commercially . Although some sources identify the song title as "History of Everything," the cover art for the single identifies the title as "Big Bang Theory Theme ." A music video also was released via special features on The Complete Fourth Season DVD and Blu - ray set . The theme was included on the band's greatest hits album, Hits from Yesterday & the Day Before, released on September 27, 2011 . In September 2015, TMZ uncovered court documents showing that Steven Page sued former bandmate Robertson over the song, alleging that he was promised 20% of the proceeds, but that Robertson has kept that money entirely for himself . </P>

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