If all goes according to plan, the world will have a new Doctor Who later today.
The show smartly introduced the concept of the title character's "regeneration" as a means of keeping things going even after the actor playing the lead role leaves.
David Tennant announced his intent to leave the series, so tonight (on BBC in the U.K., and tomorrow night on BBC America) his Doctor will presumably be killed off - and regenerate into a newer model played by Matt Smith.
The previous regeneration scene, in which Tennant replaced the outgoing Christopher Eccleston - is one of my favorite scenes in the entire run of the series, old or new. (It also features the thoroughly decent Billie Piper as "Rose").
