Simon Pegg often forgets Seth Rogen voices the alien in 'Paul' because he plays the character so well.
He has a great voice, there's a lovely ease to what he does and he's so good that I often forget it's him in the role.
The actor lent his voice to the titular character Paul, an alien who escapes from Area 51, a top-secret US military base in the Nevada desert and although Simon and writing partner Nick Frost originally imagined someone older in the role they are both trilled with Seth's performance.
Simon said: "He has a great voice, there's a lovely ease to what he does and he's so good that I often forget it's him in the role."
Nick added: "Originally when we imagined Paul he was old and angry but it was soon obvious that level of anger from any character is unsustainable for two hours.
"So the studio gave us a list of names, we had our own list and Seth was on both."
In the movie Paul hasn't gone far before he is discovered by two British sci-fi nerds - played by 'Hot Fuzz' stars Simon and Nick - who are on a road trip across the US and while the pair loved working together they admitted they don't always agree on everything.
Nick explained to movies.ie: "We're best mates and that is always more important, we'd be happy never working together again if we could stay best friends for the rest of our lives. We row a lot when we're writing and when we're not but you move on."
Simon said: "In the background is a friendship that means a great deal to both of us."