Simon Pegg once wrote a sexy poem for Sigourney Weaver.

The British actor - who stars alongside the 'Alien' actress in his new sci-fi comedy movie 'Paul' - created the prose for Sigourney in which he rhymed her name with "horny", but he refused to serenade her with it when she found out about it on the set.

Speaking on a special purple carpet at the movie's world premiere at the Empire cinema in London's Leicester Square on Monday night (07.02.11), Simon told BANG Showbiz: "I've fancied her since I was 10. I actually wrote a poem about her at university. She found out about it. She asked me if I could remember it and I pretended and said no. I rhymed Sigourney with horny."

Sigourney, 61, plays a "crackpot" woman in the film who claims to have witnessed an alien crash landing in the movie, and Simon admits they did not originally intend for the role to be played by a female.

He said: "We just gave her The Script. Initially it was a man and then we thought, 'Why don't we make it a woman?'

"We immediately thought, 'Why don't we ask Sigourney Weaver?' So we did what we normally do, we sent her the script, she read it and then we heard she had said yes."

Simon's co-star and self-professed sci-fi geek Nick Frost was amazed to have Sigourney in the film because he is such a huge fan of her in her role as Ripley in the 'Alien' movie series.

He said: "It was terrible. I sat opposite her, watching her eat a chicken caeser salad and thinking, 'She's gonna be in our film, Ripley's gonna be in our frickin' film.' This is not lost on us. We don't take this for granted. I was terrified."

As well as Simon, Nick and Sigourney, other stars who attended the premiere included Coldplay singer Chris Martin - who is close friends with Simon - socialite Jerry Hall and actress Noomi Rapace.