Attack of the Graske
Roots: The Graske looks very Farscape. The Graske needing to keep the originals alive to maintain the copies is similar to such Classic Who monsters as the Chameleons, the Autons, and the Zygons.
Goofs: If the TARDIS is following the Graske's trail, then how can it arrive before him? [It follows his trail to the right timezone and then has to wait around until he materialises.]
The map of Victorian London looks more like a map of modern London.
If the Graske want to conquer Earth by replacing its population then why does the Graske we see replace a modern day person and then travel back in time to replace a Victorian person? Why not just try to conquer Earth in one era rather than two eras?
How does the Doctor know that the Raxicoricofallapatorian is from the Slitheen family?
Continuity: It is possible to link the sonic screwdriver to a remote control, giving the remote all the powers of the sonic screwdriver. The TARDIS has an alarm which alerts the Doctor to the appearance of the Graske. Three TARDIS controls are shown. The dimensional stabiliser is controlled by a lever on the TARDIS console, the vector tracker is controlled by a small metal dial connected to a gauge (similar to a tachograph) on the TARDIS console, whilst the vortex loop control resembles a bicycle pump.
The Graske take over a world by replacing its population. They do this by materialising, and activating a hand-held device which replaces them, and then disappearing. They have to keep the originals alive in order to maintain the copies. They have time travel capability. Their planet, Griffoth, is legendary. The Doctor implies that someone caught sneaking into the Graske's base will be eaten.
The Doctor doesn't know whether he likes mangos.
The reason why multiple versions of this story exist is that it is stuck in a time loop (time loops were first mentioned in The War Games).
Links: The Doctor mentions Rose, and we see a Raxicoricofallapatorian, which the Doctor calls a Slitheen (Aliens of London, World War Three, The Monsters Inside, Boom Town).
Extras: This story has an episode of Doctor Who Confidential
Location: Contemporary Earth [probably Wales] on Christmas Day; London, Christmas Day 1883; the TARDIS; The legendary Graske planet of Gryphon.
Unrecorded Adventures: The Doctor dropped Rose off at an Abba concert in Wembley, 1979.
The Bottom Line: 'I only take the best, remember.' An "interactive" episode like this is hard to judge. It's clearly designed to amuse the kiddies rather than anything else. It has to be treated as an amusing little bit of Christmas fun rather than a serious Doctor Who story and, taken on those terms, it's a reasonable success.