It took Billy a moment to grasp Cissie's TARDIS comment. For as much as he was a general fanboy about most things geek, he hadn't yet been exposed to a lot of Doctor Who.
"Oh, it's bigger on the inside," he said with a smile once he caught her meaning. "Yeah, it took some work, but dorm rooms are terribly small and I didn't want us to be tripping all over each other between patrols and homework and extra-curricular activities."
He walked over to the small fridge and pulled out a bottle of lemonade, listening to Cissie as he did so.
"Moving, you say? I take it by the context that this isn't something you want to do?" He glanced sympathetically toward Teddy. He had no real idea about the whole story, or really any of it, for that matter.