Rory Williams is the Rani.
What's in a name?Edit
Rory and Rani: both have 4 letters, two syllables, start with an "R" and end with a "ee" sound. Coincidence, or Ranicidence?
The Mysterious ID TagEditRory is roughly the same age as Amy Pond who we know is 19 years old. Assuming the episode "The Eleventh Hour" takes place in the present day (2010)-- and this is a safe assumption as everyone is using camera phones with large screens-- then how could Rory have his ID issued in 1990 (see image below), 20 years before the episode takes place? Clearly, the only explanation is that he's a time traveller, probably the Rani.
Not to mention that Rory recognises the Doctor the minute he first sees him: nobody else does this. Time Lords can tell who other Time Lords are from a mile away. Coincidence? I think not.
Rory is unsurprised that the TARDIS is bigger on the inside than on the outside. Even given his feeble explanation that he has researched the possibility of other dimensions it seems unlikely given his characteristics that he would be able to conceal his awe. However a Time Lord would not be awed, yes?