He may not be tall, but Warwick Davis is a big man in sci-fi, fantasy and horror circles. Check out his credits, which range from “Star Wars: Return of the Jedi” (1983), “Willow” (1988) and the miniseries “The 10th Kingdom” (2000) to the title character in “Leprechaun” (1993) and its five sequels and Professor Flitwick in the big-screen “Harry Potter” adventures.

“My short stature really does lend itself to being in those sorts of projects,” says Davis, who stands 36 inches tall. “Fantasy and sci-fi are full of strange characters that quite often happen to be rather short as well.

“Fortunately, I like the work.”

Davis thumbs a ride back into the sci-fi fold with “The Hitchhiker’s Guide to the Galaxy.” Based on the books by Douglas Adams, who co-scripted the film prior to his 2001 death from a heart attack, the April 29 release casts Davis as Marvin the Paranoid Android. He’s a permanently pessimistic robot who accompanies the very human Arthur Dent (Martin Freeman) – as well as alien researcher Ford Prefect (Mos Def) and the lovely Trillian (Zooey Deschanel) – on the escapade of a lifetime after Earth is destroyed by an alien construction crew making way for a galactic bypass.

“Marvin is actually a bit heroic in this story, which I think is going to be a surprise to the audience,” Davis says, speaking by cell phone from a raucously loud pub outside of London. “I don’t want to spoil it too much, but that’s actually quite different from what people are used to.

“My understanding is that Douglas Adams wanted everything to be a little different in each interpretation,” he says, “Whether it was the BBC television series or the radio programs or this movie, which he did help write.

Photo by Laurie Sparham

PERMANENTLY PESSIMISTIC: Warwick Davis plays Marvin the Paranoid Android in “The Hitchhiker’s Guide to the Galaxy” (with Zooey Deschanel as Trillian).

“But for the most part Marvin is his usual depressed self,” Davis says. “We wouldn’t want to disappoint there. He’s very down about everything, which is lovely.

It seemed to me that it would be easy, that all I’d have to do was mope around the set,” he adds, “But as I started to work with the suit I wear, I found that it wasn’t a matter of dropping my head and hanging my arms low. That wasn’t working – it just didn’t seem to flow.

“What I ended up doing was working without the suit quite a bit in rehearsal and really feeling the emotions of the character, this utter depression, and thinking about what was making him so depressed,” Davis says. “It seems ridiculous that I had to go to such lengths and such depths for this, considering that I was in a suit, but I found it necessary.

“And it worked, I think,” Davis concludes. “Once I put the suit on, I didn’t need to perform or operate it. The movements just kind of happened on the outside. So it was exactly right and it was exactly natural for the character.”

Heading into “The Hitchhiker’s Guide,” Davis thought he’d have it easy.

He figured, he says with a bemused laugh, that he’d wander onto the set 15 minutes before the camera rolled, pop on his robot suit and be able to jump back out at a moment’s notice.

It didn’t work out that way. Marvin has a gigantic head, and that head – a fiberglass creation fashioned by the Jim Henson Creature Shop – was the signature piece in a costume that weighed a whopping 55 pounds. Davis, for the record, tips the scale at 85 pounds.

“This was the most physically demanding and difficult movie I’ve ever done,” Davis says. “The suit does weigh almost as much as I do, and just moving this thing in a controlled way was the most difficult part for me, because the weight of the suit could carry you. So, once you started walking, you had to really use a lot of force just to slow down, and to start walking again, that was a feat in itself. I got very fit.

“I also had the limitations of not being able to see anything except what I saw on the two monitor screens I had inside the suit,” the actor continues. “I had a limited view from Marvin’s perspective, from a camera mounted between Marvin’s eyes, and I also had the view from the A or B film camera – which was like working with mirrors – so I could react to people. Plus one of the Henson technicians communicated to me with a talk-back system and could describe to me where I needed to go, what was behind me, that kind of thing.

“So it was really a team effort,” Davis says. “There were actually three Henson technicians working with me, and also my friend Alan Rickman does the voice. So it’s not a one-man gig, Marvin. He’s many more people than just me.”