'Doctor Who' has never had any trouble attracting the UK's top actors for guest spots, recent years featuring the likes of Michael Gambon, Kylie Minogue and Timothy Dalton, but its greyest star might have outshone them all. We've been following news of the 2012 'Doctor Who' Christmas Special "The Snowmen" for some time, but no news has been so huge as that of Gandalf himself, Sir Ian McKellen guesting in the episode! Find out who Ian McKellen will bring to life in the 'Doctor Who' universe inside!

Fantastic, allons-y and geronimo-inducing news today, as we've just learned that 'Doctor Who' has recruited one of its biggest guest stars yet! According to the Radio Times, UK legend, Gandalf and Magneto himself, Sir Ian McKellen will make his presence known in 'Doctor Who's upcoming Christmas Special "The Snowmen!"

Rather than make an outright appearance however, McKellen will instead lend his voice to the titular killer "Snowmen," who all speak with the same voice. The special in question, airing Christmas day, will see a still-grieving Doctor allying with future companion Clara (Jenna-Louise Coleman) to take on a mysterious icy menace that plagues Victorian England in 1892.

And because of course we couldn't talk about Sir Ian McKellen without mentioning 'The Hobbit,' it's also of interest to note that Peter Jackson's hotly-anticipated prequel film trilogy features former 'Doctor Who' star Sylvester McCoy as Radagast the Brown!

Take a look at the trailer for the 'Doctor Who' Christmas Special below, sadly lacking in Ian McKellen's voice, and tell us who you'd like to see guest on the show in the comments!