As a child, Hugh Grant took piano lessons from Andrew Lloyd Webber's mother. At some point, he stopped piano lessons and subsequently forgot what he had learned. Prior to the filming of the movie, he was taught to play the portions where his hands would be visible on the keys.
Hugh Grant had to be convinced to sing himself and initially wanted nothing to do with his singing parts. After practicing and performing in the studio, he then felt so comfortable with it that he announced he would perform the big concert scene live. When it was played back, he was highly amused and humbled by how terrible it sounded and was then happy to use the pre-recorded sound.
The film's director/producer/writer Marc Lawrence offered "Dance With Me Tonight" to Hugh Grant while he was trying to find the right song to sing during one scene. What he didn't tell him was that Marc's 13-year-old son, Clyde Lawrence, had written it. On the soundtrack, Clyde actually plays the piano.
During the premiere in Amsterdam, a woman pretending to interview Hugh Grant handcuffed herself to him and ended up walking the red carpet with him.
At the top of the closing credits during the PoP! pop-up video, one of the trivia history bubbles mentions that "Colin created a huge controversy when he declared PoP to be 'bigger than The Beatles.'" This is a reference to the furor caused when Noel Gallagher of Oasis referred to the band as being "bigger than The Beatles." It also harks back to the the international controversy caused by John Lennon's declaration that The Beatles were more popular than Jesus Christ.