Three wizards and a TARDIS

He watched as they entered the TARDIS. Their wands aimed at him. He felt a smile tug, as they took in the sight that met their eyes.

3..2.. he mentally counted down, 1

"Interesting room, Spacesexpandius?"

"Yes, it's bigger on the inside..." he trailed off, as he noticed what she said. Her words should make sense to him, but his mind came up blank.

"Huh?" Was his brilliant reply.

"Spacesexpandius. You know, to make it bigger on the inside." She reminded him of somebody: of him. He closed his eyes. This was going to be a very long day.