I had a bad feeling about Paul the first moment I saw the trailer. The fainting gags. Seth Rogen's stoner schtick coming out of the head of a green man from Mars. It all just seemed so obvious for the comic duo from Shawn of the Dead and Hot Fuzz.

And as I watched the Paul promo machine rev up a sinking feeling grew in the pit of my stomach. The streak was over for Nick Frost and Simon Pegg. Paul would be a dud.

But...

Sometimes, trailers lie. (OK often they lie, but that's another blog post.) So with a sigh of relief I can happily report Paul is a gentle, goofy and occasionally filthy love letter to sci-fi fans everywhere. After all, we're talking about movie that begins at the holy grail of geekdom, the San Diego Comic-Con and ends with an Aliens reference aimed at Sigourney Weaver. Paul is the movie Fanboys aspired to be, meaning a cross-country road trip aimed squarely at nerds with phasers set on fun.

Paul, left, played by Seth Rogen, and Graeme (Simon Pegg) in comedy-adventure Paul. (Universal Pictures)

Now that we're all feeling warm and fuzzy let's deal with the matter of Seth "High Times" Rogen. In Paul, the affable Canadian lends his voice to the big-headed alien on the run from the government. A far cry from E.T. this Paul chills out in cargo pants and flip flops, has a fondness for filthy jokes and yes, likes to blaze things up once in a while. So, it's Seth doing Seth, he just happens to look like a distant cousin of Marvin the Martian.

What saves the alien-dude from derailing the entire picture are his other abilities. Behind Paul's party-hardy veneer is actual a creature of wisdom trying to help these backward beings known as humans. It also helps that Double Negative, the visual effects shop, made Paul utterly convincing. Double Negative are the same folks responsible for giving Iron Man 2 its shine and bending the building in Inception. Moving from M.C. Escher-like architecture to a walking, talking character is a big step, but Paul seems so real at time, it easy to forget he's a purely pixel-powered performance. Plus, if you don't like Rogen there are plenty of other great bit players including Kristen Wiig as a cursing Christian and a surprisingly manic Bill Hader.

Beneath the frat-boy humour, there's an obvious love for the sci-fi subculture that is the target for this film. Pegg and Frost actually did their own cross-country road trip for research and have put a lot of thought into writing the story.

Without their frequent collaborator Edgar Wright, Paul isn't as multi-layered as Hot Fuzz or Shawn of the Dead. But director Greg Mottola (Adventureland) brings a soft touch to the surprisingly sentimental story.

Rating: Three and a half glowing green dudes out of five.