Coleman made an appearance as Oswin Oswald minutes into the episode, surprising fans who had been led to believe that she would not be appearing until the Christmas special.
However, Oswald was killed off in the episode's closing moments, leaving Whovians scratching their heads as to how she will be able to make her eventual reappearance as the Doctor's new companion.
Speaking on the Doctor Who website, the 26-year-old actress said: "Boo! Hello! Hope we gave you a good surprise!
"Thanks to all the fans who kept it quiet! More to come...watch this space!"
Showrunner Steven Moffat also thanked fans: "I hope you all got a nice surprise when Jenna popped up in Doctor Who several months early. If so, that surprise came to you courtesy of the frankly magnificent ladies and gentlemen of the press, and of the many Doctor Who forums and blogs too.
"This show has been seen at four separate screenings, across four different countries and yet not one person gave one spoiler.
"From all of us on Doctor Who, a heartfelt thank you for helping us tell our story."
Watch the teaser for next week's episode 'Dinosaurs on a Spaceship' below: