Sirius stared at the Doctor. Normally he'd take a moment to appreciate the pun, but he was rather shocked by the reaction. "Animagus, technically," he corrected, as soon as his brain started working again. Relatively speaking. "...You've got no idea who I am, do you?" Of course, he doubted he would pay much attention to anything else either, if he could fly around in a magnificent ship like the TARDIS.