Doctor Who” fans were saddened this weekend to learn that Matt Smith is departing the TARDIS for the last time, stepping down as the 11th Doctor in time for the character to “regenerate” just after the show’s 50th year on the air.

It’s not clear who will replace Smith, but the Internet is running wide with speculation. Variety’s Steve Clarke reminds us that Helen Mirren could be the first female Doctor, but says bets are also on “Harry Potter’s” Rupert Grint and “Being Human’s” Russell Tovey … or a lesser-known actor, like Smith was himself.

But who do you think should fill that phone booth? Vote below: