The funniest comedy team in the world is back.

Real-life best friends Simon Pegg and Nick Frost first worked together on the British television series "Spaced," then made two of the best comedies of the past decade, "Shaun of the Dead" and "Hot Fuzz."

Those films did only moderate business in the U.S., partly because British comedies usually struggle here and partly because the movies didn’t benefit from an aggressive marketing campaign.

The actors have built a devoted fanbase here, though, and now "Paul" gives Pegg and Frost their best shot at a genuine hit in America.

They are also in their natural habitat for this story. They co-wrote the script and play the lead characters Graeme (Pegg) and Clive (Frost), English sci-fi geeks who attend Comic-Con then embark on an RV pilgrimmage to visit famous UFO-related sites.

Pegg and Frost were born to play these roles. They are, rather famously, bona fide pop culture and sci-fi geeks. That authenticity translates on screen into one of the strongest points of the movie.

As fate would have it, Graeme and Clive’s road trip is interrupted when they encounter an actual alien named Paul, voiced by Seth Rogen.

Consciously defying the usual movie representations of aliens, Paul is neither a colonizer nor a cherubic healer. He wears Birkenstocks, shorts but no shirt and a backpack. Paul is a wise-cracking slacker alien, and Rogen is the ideal choice to voice him.

Paul has been detained secretly since — you guessed it — he crashed in 1947, but now he is trying to get back home. He escaped from a government facility and is on the run from black-suited government agents who must capture him at all costs.

Graeme and Clive of course change their plans and decide to help Paul, despite being chased by ruthless Agent Zoil (Jason Bateman). Bateman plays the role straight, menacing and completely against type.

Also joining the pursuit are a couple of newbie agents, Haggard (Bill Hader) and O’Reilly (Joe Lo Truglio), who are as idiotic and slapstick as Zoil is focused and stone-faced.

All three agents take orders from a supervising agent they call The Big Guy. We don’t see The Big Guy until the film’s climax, but any science fiction fan will recognize the voice.

Graeme, Clive and Paul pick up a fourth passenger along the way, a fundamental Christian named Ruth (Kristen Wiig).

This is unfortunately yet another movie that stereotypes Christians as fanatical zealots, but Wiig compensates by being hilarious and infinitely likeable.

Ruth has been extremely sheltered, and once Paul enlightens her to his existence and all it implies about the history of the cosmos, she decides it’s OK to do things like drink and swear. However, she’s new to cursing, and her failed attempts to do it properly become one of the funniest running jokes of the movie.

As screenwriters, Pegg and Frost display the extensive knowledge of science fiction movies for which they are known. They inject cameos, references and borrowed dialogue from many sci-fi classics.

That’s fun for fans, to a degree, but the movie works better when they aren’t quoting past films, and the references rarely go beyond the mainstream. "Paul" isn’t a film-geek movie, in other words, which is good or bad depending on your opinion.

As comedians, Pegg and Frost are as funny as ever. Theirs is a completely natural chemistry, and it’s a joy to watch.

The key differences between "Paul" and other Pegg/Frost films result from the director, Greg Mottola. It’s the first time Pegg and Frost have co-starred in something not directed by Edgar Wright, and it shows in the style.

Mottola wrote and directed "Adventureland" and helmed "Superbad," and while his style isn’t as unique as Wright’s, Mottola probably has a better sense of character.

"Paul" doesn’t equal the ingenuity of Pegg and Frost’s previous work, but it’s great fun and likely to be one of the best comedies of the year.