...well, there are those Vortex Manipulators. So there's clearly other ways to do it. Plus all those aliens trying to kill The Doctor have to keep up.
The Impossible Face thing, right? My Doctor looks different too and I never met you or Rose.
But the TARDIS, the time travel, the same feel, some of the same little quirks, and honestly, The Doctor I know is over nine hundred years old. I wouldn't be surprised at all if he was changing faces somehow. He is an alien.