Going off on a tangent here, this double episode set the parallel universe signifiers for another show, Fringe, that stated airing a couple of years later. The Zeppelins in particular, but also the in-ear headsets (although without the Cyber-implications) and the need to carry identification.

The later development, from "Doomsday", that crossing over impacts the stability of the parallel universe, also comes into play in Fringe. The Zeppelin escape scene from the episode discussed here is copped almost verbatim in season 4 of the latter show — with Cybermen substituted by zombies.

There is also a time travelling character whose apperances are telegraphed pretty much the same way that Clive (RIP) presents the Doctor in "Rose". It would be shameless, if the creators and writers of Fringe weren't gleefully and openly borrowing from pretty much every scifi-adjacent show out there.

X-files and Twin Peaks are directly referenced more than once, and there are obvious callbacks to Cronenberg's The fly, as well as The Manchurian candidate, Firestarter, Altered states, and more.

Tangent over, the scheduled discussion will continue as planned.