13 Doctor Who Guest Stars Who Were Tragically Underused

2. Sir Ian McKellen

You knew he'd be included on this list at some point! Sir Ian McKellen made Doctor Who's 2012 Christmas Special even more so when he lent his voice to the episode's antagonistic Snowmen but, in a similar vein to Imelda, it's a real shame that he wasn't given a bigger part to play in the festive proceedings. As iconic and recognisable as his voice is, Sir Ian would be a welcome edition to the show's plethora of veteran guest stars and he's already a beloved household name for his portrayal of Gandalf in Peter Jackson's acclaimed Lord of the Rings and Hobbit trilogies. The show has already played host to Michael Gambon (Dumbledore in Harry Potter) so it's only fair that it offers the spotlight to another of fantasy's most notorious wizards, too. It's not all bad news, though, because there's still the chance that Ian will return to the franchise one day in a much bigger way and the truth of the matter is that it would be a wasted opportunity if he doesn't. Speaking of Doctor Who alumni who also happen to have received knighthoods, there's still one other guest star to go...