Peter quirks an eyebrow up at his introduction, but doesn't comment. Just 'the Doctor'? Of course questions of 'Doctor of what?' come to mind before who actually, but that's all pushed away when the Doctor says that his best friends are behind that door. The expression on Peter's face is one of sympathy. He has found a door home and he can visit his aunt, but he can only imagine if he couldn't, if he was separated from her.

"There could be another door, to before this, before the angels got there." He's hoping for the Doctor's sake, but in some ways, he's also hoping for himself. There's a chance he could see Uncle Ben again if he can find a door to earlier.