I think the girl they got to play Trillian in The Illustrated Hitchhiker’s Guide to the Galaxy looks the part. Her name is “Tali”. Beyond that the only thing I know is that she looks good with Zaphod’s third hand on her bum.
I think Hoskins would be MUCH better as L. Prosser :D.
Arthur Dent has to be a British actor that can play ‘sheepish’. I’m not sure who, but I really don’t see Hugh Grant in that role.
Those guys are perfect for Majikthise and Vroomfondel, though.
Just posting to add, right now this thread has 42 replies. Of course I’m making it 43… 
Twiddle
Ya know, I actually think this is a pretty good suggestion. (Owen, not Jackie.) I’d hate to see them make Arthur (or any of the characters) American, but I also think that there is something about the book (and the radio show, in fact) that just wouldn’t work as a movie. A straight, faithful, Peter Jackson-style translation to film would be disasterous, in my opinion. I can’t quite explain why, but watching the TV episodes might give you some idea. The key is for the movie to find its own vibe. That Wilson-brothers drollness would be different from but compatible with Adams’ style, and could be just the thing to give it the perfect cinematic groove. I wonder if Owen does accents?
Mr Rickman would be perfect for the Vogon Captain can’t you imagine the following?
See, see the ageing sky
Marvel at its big peuce depths.
Tell me, Cecil do you
Wonder why the cat or dog ignores you?
Why its foobly stare
makes you feel alive.
I can tell you, it is
Worried by your frinjle froom facial growth
That looks like
A mouldy leftovers.
What’s more, it knows
Your frontage potting shed
Smells of very small apples.
Everything under the big grey sky
Asks why, why do you even bother?
You only charm dogs.
How about Peter Sallis as the voice of The Book? He did the voice of Wallace in the Wallace and Gromit short films.
No, too querulous. The book should sound confident…especially when it’s misleading the reader.
Whoever plays Arthur has to be able to deliver this line with a perfect deadpan:
“Ah. Abuse.”
I like the idea of Jack Davenport (if that’s the guy who played the Commodore in PotC) playing Arthur.
No Jim Carrey. Anywhere near this film.
Ian McKellan would make a fine Slartibartfast. Or maybe a cameo as that prophet who shows up too late at the Restaurant at the End of the Universe.
Speaking of PotC, why don’t we make Zaphod, Johnny Depp. I’m sure Depp can capture that crazyness :D.
Okay. I’ve read the books. I’ve got the TV series on one (low-quality) videotape. I’ve even got the original radio show (minus the “this robot can hum like Pink Floyd” bit, alas) on audiotape. And this is all that I have to say.
All of you who are suggesting American actors for this are nuts. Even if said actors can pull off British humor.
R.
Well why do aliens have to speak with a British accent? 
I can see Arthur, Trillian, and Ford speaking that way (Ford because he has to blend in), but Zaphod and Slartibartfast don’t.
I can definitely get behind Jack Davenport (and yes, he WAS Commodore Norrington in POTC) as Arthur and Bruce Campbell as Zaphod. Johnny Depp could be Ford Prefect.
Then again, Johnny Depp could play pretty much anybody, including Trillian. He could put on a one-man production if he wanted to.
Maybe Dustin Hoffman could be Arthur?
Johnny Depp as Zaphod is…acceptable.
Can’t agree with Hugh Grant as Arthur. The only remarkable thing about Arthur Dent is that he is remarkably “un-remarkable”. While, being a guy, I don’t have any partcular opinion on Hugh Grant’s appearance, the fact that he seems to inspire a great deal of swooning among female moviegoers would automatically disqualify him from the role. Sorry, girls.
If you make The Hitchhiker’s Guide less English, it becomes less The Hitchhiker’s Guide. If they cast an American as Ford Prefect, they’ might as well change the character’s name to Ford Tudor, too.
(Damned contemporary American models and their equally English-sounding names spoiling my point!)
After thinking about this all day, it seems to me that Eddie Izzard might make a better Ford than Zaphod. Ford is somwhat more sophisticated than Zaphod and I think Izzard would do well. Zaphod needs a “Smooth but stupid” actor of which many might fill the role. I still like the Idea of Hugh Grant as Arthur. I would hate to see Jim Carrey as anything but I don’t think it would stop me from seeing the film.
If any of The Restaurant is included, Rowan Atkinson has to play the Maitre d’ and have Ozzy as the rock star.
How about Dawn French as Eddie, the unbearbly cheerful computer?