There are some iconic roles in movies and television that you can't imagine anyone else playing. Like can you really see anyone but Bruce Willis playing John McClane in Die Hard? Harrison Ford is basically perfect as Han Solo, as well as Indiana Jones (except in that fourth movie, that one sucked).
One of the best TV shows out there right now, whether you are watching it or not, is Breaking Bad. Bryan Cranston is remarkable as a chemistry teacher-turned-drug dealer, so good that he has three Emmys on his fireplace proving that fact. The fifth season premiere Sunday night was the most-watched episode of the series, drawing in 3.5 million viewers, a very impressive number for a cable channel like AMC.
The success that Cranston is having with the series make it surprising that he was not the first choice to play Walter White. Heck, he wasn't even the second choice. According to this report from the MSN, Cranston was the third choice...behind Matthew Broderick and John Cusack. Could you imagine Ferris Bueller or the guy from Say Anything really portraying the character that Walter White has become, instead of Cranston? Me neither.