There are no fat aliens worth a damn*. Sorry Baron Harkonnen, Boss Nass and Jabba, but true sci-fi chic comes from abstention from marsh minnows. However a strict diet is not enough - true alien-appeal comes from high cheekbones and piercing (usually blue) eyes set above a noble and narrow nose. Keanu Reeves has the stuff to play 'alien' - which he's now doing in The Day The Earth Stood Still - and here are some more other-worldy physignomies from Hollywood past and present…

10: Peter Weller

The first pre-requisite of any actor playing a cyborg is a wiry and almost non-existent physique, since this allows make-up artists to build up prosthetic cybernetic sections where the muscles (and, indeed, fat) would be on most people. But Weller's gaunt face betrayed his reed-like form in Robocop, and you get the feeling he had room to knit a sweater inside that outfit. Other sci-fi credentials include The Adventures of Buckaroo Banzai Across the 8th Dimension (1984) and Screamers (1995).

9: Bruce Spence

Initially famous outside of Australia as the wonderful chopper captain in Mad Max 2, Hollywood's partial relocation down under has given new zest to Spence's career, and he's next to be seen with Hugh Jackman and Nicole Kidman in Australia (2009). But it was in Revenge Of The Sith (2005) that his slight frame gave the costume and make-up department of George Lucas's final prequel a chance to create an extraordinary effect without a computer. With the Matrix films, Queen Of The Damned, Farscape, the Lord Of The Rings trilogy and many others under his belt, Spence knows when he's onto a good thing.

8: Keanu Reeves

It's hard to believe that any actor so unearthly in appearance could have kick-started their career as an IQ-challenged stoner in the Bill And Ted adventures. It's in sci-fi such as Johnny Mnemonic (1995) and the Matrix trilogy where the Beirut-born actor sits most comfortably, and his legendarily impassive face is a good substitute for Michael Rennie's as new Klaatu.

7: Keir Dullea

The unlucky astronaut of Kubrick's 2001 was to reprise his role as a ghostly figure in Peter Hyams' monstrous 2010 (1985), but his unearthly physiognomy made a lot more sense as a ghost. He also played a Christ-like stranger from the future in TVs The Next One with Adrienne Barbeau.

6: Michael Rennie

English-born Rennie, the originator of the extra-terrestrial role played by Keanu Reeves in this month's remake of The Day The Earth Stood Still, went on to play other unworldly figures such as the template for Michael Biehn's Reese in Cyborg 2087 (1966) and St. Peter in The Robe.

5: Robert Patrick

One wonders if James Cameron hired such a thin actor just in case the seminal CGI of Terminator 2: Judgement Day didn't work out, and the production might have to resort to the old prosthetics sleight-of-hand. But Patrick has such a narrow yet well-proportioned face that you might imagine those slightly obtruding ears were stuck on to make him look like the rest of us. It didn't work, and this very nice man has continued to work regularly in sci-fi since playing the T1000, when not participating in more earnest fare such as The Unit and Copland (1997). His most committed return to the genre was as central sceptic John Doggett in the final two seasons of The X-Files.

4: Cillian Murphy

Super scary Cillian is almost destined to play crazy or strange; he was good in 28 Days Later, but his ethereal stare provokes the thought that he's harbouring some secret strangeness, or is about to sprout tentacles or talk to God. Therefore lucrative 'straight' roles may be scarce should they ever prove interesting to him.

3: Jude Law

With a clear and piercing off-world gaze, and that 'designed-in-Poser' facial geometry, Law was a clear choice for the role of a 'perfect' cybernetic Gigolo in Kubrick & Spielberg's A.I.: Artificial Intelligence.

2: Robert Powell

For my generation, the face of Jesus. In Franco Zeffirelli's extraordinary 1977 adaptation of the new testament, Holby City's Powell was (sorry) a miraculous piece of casting, with a commanding voice and presence to match up to a set of cheekbones that were almost above his forehead. Shortly after, Powell played another mysterious part as the Rasputin/Christ figure in the under-regarded and very odd Harlequin (1980), and had already played Tommy's ghostly father in Ken Russell's 1975 rock-opera.

1: David Bowie

With his early 70s sci-fi obsession, Bowie was a shoe-in to play a dispossessed off-worlder in Nick Roeg's fascinating but confusing The Man Who Fell To Earth (1976), and later adopted the robes of the new testament - as many an 'alien' actor does - to play Pontius Pilate in The Last Temptation Of Christ (1988). He rounds off an eccentric career with such roles as Jareth The Goblin King in Labyrinth (1986) and jilted John, the vampire eschewed by Catherine Deneuve for Susan Sarandon in The Hunger (1983).

* I'm not speaking from the high ground here.

Top 150 actors that resemble each other
Top 10 actors playing themselves
11 actors who 'gave up acting'
10 inappropriately bad acting performances