'Doctor Who' (Sat., 9PM, BBCA) season 5 premiere
It's the debut of the new 'Who,' as in Matt Smith, the previously mostly-unknown actor who replaces David Tennant as the newest driver of the TARDIS. Smith, who actually made his first appearance in the franchise in January's 'The End of Time,' Tennant's last 'Who' hoorah, is the 11th actor to take the lead role, and, at 27, is also the youngest Who ever. But that doesn't mean he gets time to ease into his new gig ... in fact, in the season premiere, he's thrown into a situation where he has just 20 minutes to save the world, and he has to do so without the TARDIS (which was wrecked during the regeneration of Tennant's Who into Smith's Who) and the sonic screwdriver, which has gone "wibbly-wobbly." Good thing he meets his new companion, Amy Pond (Karen Gillan), just in time to help him through his pressure-packed journey.

Recasting 'Doctor Who' must be like recasting James Bond: you have to get it right or serious fans will be really irritated. Here's a look at the new Doctor (Matt Smith) in action. The new season starts Saturday, April 17 on BBC America. You probably can't tell a lot from just a trailer, but what do you think?