Mark Hamill voices an alien in 'Star Wars: The Last Jedi' as well as playing Luke Skywalker.

The 66-year-old actor appears as the Jedi Master in the eighth instalment of the popular sci-fi franchise but he also lent his voice to a CGI character known as Dobbu Scay.

However, Hamill has refused to give any more details about his new character because he loves ''the mystery of it all''.

Speaking at a post-screening on the movie, Hamill said: ''I don't know what you're talking about. I'm not telling. I like playing the mystery of it all. I said I'd love to do a CGI thing and he said sure. And I got to go to the set of the casino and see in detail 150 extras in jaw-dropping costumes.''

Hamill is a veteran voice actor having won numerous plaudits for voicing The Joker in 'Batman: The Animated Series' and numerous feature length animations based on DC Comics stories, including 'The Killing Joke'.

Although Hamill shot to fame in the original 'Star Wars' trilogy as Luke Skywalker, he recently admitted it may have been more fun to play Darth Vader or Han Solo, although he likes playing ''bland'' Luke because he is the ''one centred character'' to be a contrast to all the other characters in a galaxy far, far away.

He said: ''When I first read the screenplay of 'A New Hope', I felt it would be much more fun to play the cynical pirate who's always making wisecracks or Darth Vader, who has such an interesting role, or C-3PO, who is hilarious. Luke is so bland! He doesn't have as much colour as the other characters.

''But it's like Dorothy in 'The Wizard of Oz' - there has to be one centred character to provide contrast to all the other characters around them, even if I would rather play the Cowardly Lion or the Tin Man or even The Wizard than Dorothy.

''And Luke makes people feel at ease. He's not scary like a pirate. He's not spectacularly talented or super intelligent, he is just an average farm boy. And that is a nice thing.''