Dr Who Christmas Special ...

[osprey]

How was it possible for the Titanic to penetrate the TARDIS ? I always thought it was impenetrable.

[Joe Shmoe]

Hello Osprey , As I understand it The TARDIS is impenetrable when it has materialised and in a solid state. But When it has de materialised and is travelling through the time vortex it is no longer solid it can be penetrated. This has happened before in the episodes "The Parting Of The Ways" and "The Runaway Bride" I hope that makes things clearer for you.:-D

[Llamatron]

Sorry to be the one to break it to you but it's not real.

They can make can make it do whatever they like.