Space alien advocate Kiefer Sutherland

Kiefer Sutherland believes in aliens. The 42-year-old actor - who voices the character of General W.R. Monger, a military man who is delighted when his band of incarcerated monsters are used to fight an alien race invading Earth - also revealed he was nervous about attending the premiere in the UK capital. © Solarpix / PR Photos

The 42-year-old actor - who voices the character of General W.R. Monger, a military man who is delighted when his band of incarcerated monsters are used to fight an alien race invading Earth - also revealed he was nervous about attending the premiere in the UK capital. © Solarpix / PR PhotosThe 'Monsters vs Aliens' star is adamant there are life forms on other planets and cannot understand how people can think humans are the only intelligent race in the universe.Speaking at the UK premiere of the animated movie in London's Leicester Square last night (11.03.09), Kiefer told BANG Showbiz: "Maybe aliens don't exist in the form they take in the movie, but I think it would be pretty arrogant to think that we are the only people or things in the universe."The 42-year-old actor - who voices the character of General W.R. Monger, a military man who is delighted when his band of incarcerated monsters are used to fight an alien race invading Earth - also revealed he was nervous about attending the premiere in the UK capital.He said: "I'm a bit nervous to be honest. I don't think I've seen this many people for a single event in a long time. I'm just about breathing properly again."Kiefer walked the specially created blue carpet with his co-star Reese Witherspoon - who voices Susan, a woman who grows to 42ft 11ins when she is hit by a meteor - and both spent time signing autographs and meeting fans.Joining the stars on the carpet were two of the monsters from the film - a woman on stilts delighted fans by appearing as Susan, while a super-sized version of the gelatinous B.O.B also posed for pictures.Kiefer admitted making the movie was unlike anything he has ever experience before, but came as a welcome relief from his role as tough guy Jack Bauer in US TV show '24'.He explained: "I was making '24' when we made 'Monsters vs Aliens' and just to be able to get out of the grind of what '24'can be and spend six hours joking around, laughing, trying to be funny, it was such a breath of fresh air."The actor also cleared up one of the great mysterious of '24', saying:"Does Jack wear a catheter? No, he does not. He uses the restroom when they're shooting other scenes."