Doctor Who: 12 Cool Details Russell T Davies Just Revealed About New Earth & Gridlock
8. The Potions Originally Killed All The Patients, But Steven Moffat's Comments Inspired A Happier Ending
Near the end of the episode, the hospital is overrun by an army of diseased humans, but of course, the Doctor saves the day: he mixes every single intravenous solution he can find into one big concoction, and sprays it over those who are infected. Job done!
This leads to a happy ending in which everyone is cured and the diseases are contained, but in Davies' first draft of the script, things concluded in a much darker fashion: the infected humans all died. Grim.
But then... enter Steven Moffat. The famous Doctor Who writer and showrunner remarked that Davies loves killing off his characters, which prompted Davies to change his script and make the ending a lot more cheery.
Steven Moffat? The guy who's known for killing everyone? Well, almost everyone. He was responsible for a happy ending in which everybody lives? Madness.