1. A Fashion Accessory That Alternates Between Two Colours, Depending On Whether Or Not The Episode Is In The Past Or The Future, Respectively
One of the lesser known tidbits of trivia from the Whoniverse is that both Ten and Eleven's clothes changed if the episode was in the past or if it was in the future. Ten's suit alternated between brown and blue, while Eleven's bow tie was red for episodes in the future and blue for episodes in the past. Having the Doctor vary his outfits a little bit between each episodes is a great way to add some more visual variety, and keep the show looking fresh. Regardless of whether any of these predictions come to fruition, I know that the BBC will do a great job casting the role.