The Willow actor will appear in Neil Gaiman's forthcoming Cybermen episode and had previously admitted that appearing on the sci-fi drama would be a "dream".
"It was a great thrill to be in Doctor Who," Davis told SFX. "A career ambition. But to be in an episode written by Neil and to have Cybermen in it, was for me the jackpot.
"I was one of those kids who hid behind the sofa, so I know they are scary. But the Cybermen that I saw were awesome and yeah, I think it'll be scary."
The Life's Too Short star also praised "amazing" Who lead Matt Smith.
"He's so full of energy and spark and imagination," Davis said. "You read the scene on the page and you think, 'That's a good scene', but Matt gets hold of it and it's... incredible."
Former EastEnders star Tamzin Outhwaite and Being Human actor Jason Watkins will also appear in the Gaiman episode, which forms part of Doctor Who's forthcoming eight-part run.
The series returns to BBC One on Saturday, March 30 and will premiere the same day on BBC America in the US.
> Doctor Who Steven Moffat on 2013 episodes: "We've gone all-out"
Watch a trailer for Doctor Who's 2013 episodes below: