When it comes to amusing interviews, you can't beat a bit of Simon Pegg and Nick Frost. If you put them together in a press conference with Kristen Wiig, Sigourney Weaver, Joe Lo Tuglio, Jason Bateman and director Greg Mottola, you've got the greatest roomful of funny people since the film Paul. Which, by an coincidence, is exactly what they were there to talk about.

Comprising of Arrested Development actors, sci-fi geeks, Adventureland directors and movie legends, the ensemble spent a lot of time throwing around entertaining in-jokes. Here's what they had to say about aliens, Christians, and Steven Spielberg...

Who's your favourite alien?

Jason: Apart from Paul? The Stay Puft Marshmallow Man! Does he count?

Joe: Alien. I'm a purist.

Greg: I'm gonna go with... Yoda. I'm extremely dorky.

Kristen: Is Chewbacca an alien? (Laughs)

Simon: In Starship Troopers, when they're attacking the base, about 5 rows back on the left... that guy. He was just giving it a little more than the others. (Laughs)

Sigourney: I always liked the Pod People. The version of you that's completely humourless. Suddenly you have a face like that, but your spouse can't tell.

Nick: The 58 or 73 version?

Sigourney: I like them both!

Nick: I think... E.T!

Was writing the script a case of building it around the cast cameos?

Simon: You want to play to everyone's strengths, but in terms of lines, the most famous is Sigourney's "Get Away from her," which Ruth says and we asked Sigourney if we could use it against her and she was like "Bring it on!" (Laughs) She gave us a reading of the line and Nick and I were just geeking out...

How did you create a sense of Paul actually being there on set?

Greg: Seth was shooting The Green Hornet, so we couldn't have him on set. So we recorded Seth doing the scenes with Nick and Simon in pre-production, then Joe watched the tapes and improv-ed. That's a big part of why the film has life to it - it doesn't feel like they're standing around talking to a stick with two ping pong balls for eyes.

Joe: I was on my knees for most of the shoot but still kept my dignity! It was great to work with Simon and Nick for two and a half months - I've been such a fan of theirs since Shaun of the Dead - and get to be both the stand-in and play O'Reilly, who's just a fanboy with a badge. For him, this is probably the biggest thing since Lethal Weapon 2 came out.

How important is a sense of peril in a science fiction movie? Were there studio objections to the dog's fate?

Simon: It's important to have some peril or there's no sense of danger. Something has to be at stake. When they get hold of Paul, they want to scoop his brains out.

Jason: Does the dog die? I thought he gets abducted!

Simon: We hear him scream out in pain and agony...

Jason: That's enlightenment! New life! (High-pitched dog voice) I'm going on a trip! (Laughs)

There's a strong anti-creationist joke running through the film. Do you think you'll get flack from the Bible Belt?

Nick: Who doesn't get flack from the Bible Belt?! (Laughs)

Simon: If you have faith, a film about a dope smoking alien isn't going to change that! (Laughs) We were just really interested in the angle that your beliefs can be shaken by a single moment. And that's why Ruth is a creationist, as opposed to a specific type of Christianity. You can't have a film with an alien in it without it being anti-creationist. It's not being anti-religious, it's just the universe the film is set in.

How big a part does Nira Park play, especially with Edgar Wright absent?

Simon: Nira's our longtime collaborator and a great friend. We work out of Big Talk, her production company, and she's a very important mentor and creative collaborator. She's an extraordinary presence. We love Nira, and will continue to work with her... forever.

Kristen, how was it coming up with new swear words in the film?

Kristen: There was a lot of talk about alternate words...

Simon: Butt horns...

Nick: Baby with a hard on...?

Jason: That's the name of a my production company! (Laughs)

Simon: It was a case of getting disparate words and putting them together. Ruth is learning so she comes up with "Get away from me you stupid vaginas!" That's a great one.

Nick: Here in Britain we have a great heritage of swearing. I remember asking a Danish friend what was the word thing he could say. He thought for ages and came back and said "It's long-haired communist fag." (Laughs)

Sigourney, you must get a lot of offers for Alien-based cameos. What made you accept this one?

Sigourney: I would be quite careful of that. I love the Alien franchise, but this was done within a context that I found sort of believable. If it wasn't in the hands of Greg Mottola and the other guys, I wouldn't have wanted to do it. My one worry was that it wouldn't be very organic, but I knew they would do it seamlessly.

Do you think there's a female role in comedy given the male-centric films made these days?

Kristen: Definitely for this movie, it was something different. A lot of time, the female role in a comedy is the nagging wife or crazy neighbour. They actually thought about her character.

Sigourney: I think a good comedy is very hard to find. It's true there aren't as many female-driven comedies about women being goofy and irreverent, but I think that will come.

Was it a challenge to pay homage to Spielberg's sci-fi classics?

Greg: There were a lot of things I had to do here that I had never done before. Like show up to work sober. (Laughs) I grew up at the perfect time for being a Spielberg fan. I can't pretend I could ever touch his technique, but strangely I ended up watching Sugarland Express and Duel more than the obvious ones like E.T. and Close Encounters.

What was it like directing Spielberg in his cameo?

Greg: We were shooting Seth with multiple cameras, so I was waiting for them to signal the cameras were all ready so I could call action. I missed it, so I'm waiting, everyone's waiting and Steven just says "Can I start?" I blew it, but I had to give him direction and he got better, so I directed Spielberg very well!

Jason, how much did you enjoy playing an action man with a gun?

Jason: It was a lot of fun. I don't often get to play that guy. Joe and Bill were doing such great comedic work that you need a straight man. This guy was written as virtually expressionless, so my job was easy, besides having to keep a straight face.

Simon: We were adamant that Zoil be played by someone who was a credible threat, who wasn't a comedic actor. Jason's one of the few people who can do both sides convincingly. In a show like Arrested Development, he's the straight man but he's also one of the funniest characters. It's a rare gift.

Paul is released in cinemas on Monday 14th February.