Cast in J.J. Abrams' ambitious "Star Trek" reboot, Simon Pegg is about to engage in a five-year mission to boldly go to the farthest reaches of the known and unknown galaxy.

But whatever the crewmembers of the USS Enterprise find — whatever alien life forms they happen to come across — it won't be as out-there as the character Pegg plays in "Run, Fatboy, Run," Pegg said with a laugh.

"He's slightly less believable than most science fiction," Pegg joked of Dennis, a layabout who jilts his pregnant wife (Thandie Newton) at the altar in the film's first scene. "That I, me, 'Potato Head,' would leave the most beautiful woman in the world at the altar while she was with child ... this guy is an idiot!"

In the film, Dennis attempts to woo her back by competing in and finishing a London marathon, building his stamina on a heavy diet of "lager and curry," Pegg explained.

But it's Pegg himself who seems to be running a movie marathon these days, sprinting from one gig to the next as a suddenly in-demand star. First and foremost among them, of course, is "Trek," in which Pegg will play chief engineer Montgomery "Scotty" Scott.

Despite his heavy geek cred, Pegg's casting was greeted as an unusual choice when it was announced late last year since, among other things, he ain't exactly Scottish. Never mind that: Pegg reassured "Trek" fans that their franchise is in good hands.

"I think the key thing for the 'Star Trek' fans out there that might be a little concerned about what the film is going to be [is that] it's written by, directed by and performed by fans," he said. "There's no need to be worried. [J.J. Abrams is] the kind of person you'd want. If I was a fan of something, I would want the person doing the new version of it to be similar to me — and J.J. is that."

It's a talented crew of actors who, in many ways, have come to mirror "the ultimate space family" they play, added Pegg.

"That's the beauty of 'Star Trek.' It's an ongoing story, a continuing voyage," Pegg mused on the possibility of "Trek" sequels. "[I'd like to see] more engagement with those characters. There are so many great relationships going on."

But at the same time Pegg and company will be cavorting across the universe on the big screen, he'll be sharing a very different kind of trip in real life, he revealed, journeying across America with longtime partner-in-crime Nick Frost in "Paul," a movie that will mark their collaborative screenwriting debut.

"It's a road movie about two British geeks who are traveling across America. They've been to Comic-Con and decide to branch out into the interior a little bit," Pegg said of the flick's setup. "Hilarity ensues."

Pegg and Frost, of course, are best known as the co-leads in "Shaun of the Dead" and "Hot Fuzz." But Pegg's never had as much fun with Nick as he did writing "Paul." "[It's] the most happy I've ever been with a first draft," he said.

After "Paul," Pegg and Frost aim to reteam with their director of choice, "Shaun" and "Fuzz" helmer Edgar Wright, for the third and final film in what they've been jokingly calling the "ice-cream trilogy."

"We have an idea that we're really excited about that will probably be the logical conclusion to the first two," Pegg said. "We're hoping that with the success of the first two, we're going to get more resources and be able to realize it, because it's a pretty ambitious idea."

That Pegg is excited about so many upcoming projects seems unfairly drowned out in recent days because of how upset he is about one in particular, an American remake of his hit BBC show "Spaced."

"I don't know about it being doomed to fail, I just don't think it's necessary. It's a very personal show and every single joke in that first episode has grounding in a personal experience and reality for myself and [co-star] Jessica Hynes," Pegg contended. "To have someone just appropriate it and reuse it somewhere else feels a little bit weird.

"We've tried to be as dignified as we can about it," he added. "But for a group of people who profess to be huge fans of the show, the fact that they didn't think to ask us what we thought seems to me to be a gross oversight and a mark of extreme disrespect."

And, just like that, Pegg suddenly needed to run off again. "Run, Fatboy, Run" opens March 28.