McMullen says of his casting,
"My agent’s assistant put me up for it. He thought it would be something I’d enjoy.But what does Nathan think of working with the other actors, especially Peter Capaldi? He says:
I’m not a die-hard Whovian fan so I did my research, went for the audition and a couple of weeks later I got the call. I was like ‘brilliant!’
It’s a bit of a funny one – I literally can’t say anything. I’m sworn to secrecy!"
"Peter Capaldi is brilliant in anything he does.The as-yet-untitled Christmas special will be aired on BBC One and BBC America on Christmas Day.
I was excited to be able to work with them [Capaldi and Nick Frost]. But you’re there doing a job at the end of the day so you can’t be overwhelmed.”
[Source: Liverpool Echo]