4. Hugh Jackman - Wolverine - X-Men (2000)
You might not remember the circumstances surrounding Hugh Jackman's casting as Wolverine in the original X-Men movie, because he seems like a perfect match in retrospect, and it happened a long, long time ago, but let me refresh your memory: everybody was super confused when they found out he'd been cast, and for one major reason. Who the hell was Hugh Jackman? An unknown actor, cast three weeks before filming as a replacement for Dougray Scott - that's who. Given the circumstances, then, I suppose you can sort of understand why there was something of a panic regarding this one: fans were worried that some random guy was going to spoil their chances of securing a great big screen Wolverine. Fortunately for everyone (especially Hugh Jackman, whose movie career was made by this role), the actor channeled everyone's favourite X-Man perfectly, and has been reprising the character in every second movie ever made since.