The Doctor Who universe is vast and incredibly infinite, much like the TARDIS itself, wherein the titular time traveller and his companion encounter all types of people and come across a heap of knowledge about planet Earth's culture along the way. The Doctor has referenced some of these pop cultural classics throughout the course of his travels, such as Harry Potter and Back to the Future. However, what if these other worlds, which everyone has seen on the television and in cinemas, could be transport into the Whoniverse itself? In this article, 10 almighty and significant - and not to mention oh so addictive - fantasy worlds will go under the spotlight. Why should these legendary franchises come across the Doctor and his wonderful universe? This list will delve into why they would work and also why some (or maybe even all of them) wouldn't quite lend themselves to the perfect Who crossover. It's always best to look at both sides of the spectrum, after all. The obvious and endlessly demanded crossovers are mentioned as well as a few unusual and interesting ones to mix it up a bit. And yes, this list does include a few cartoon favourites, too. Because why the hell not?