This episode is just plain fun. Cassandra the skin flap makes an unexpected return, and her possession shenanigans give David Tennant and Billie Piper the opportunity for some wonderfully silly performances. On the other end of the tonal spectrum, Cassandra's sendoff is genuinely quite compelling for a character who was introduced as being a "love-to-hate"-type antagonist at best. Additionally, the makeup on the cat nurses is astonishingly good, especially for such an early episode in the revival. Does the solution to the sick-clones make sense? Not really. Do I wish we'd gotten more of a look into New (New New New New...) New York proper? Certainly. But for all the episode's shortcomings, it's carried by its tight pacing and great character banter.