These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Accidental Innuendo: The phrase 'glory hole', which carried an entirely different connotation in the UK at the time (it referred to a cupboard under the stairs. Make all the Harry Potter jokes you like), is repeated throughout. Please accept this fact and move on.
Ensemble Darkhorse: Dr Emilio Sylvestri. In the commentary, the creators note that at film school screenings he always gets an immediate positive response.
Gone Horribly Right: In some respects, as Kimmy illustrates, Pipes gave everyone watching exactly what they wanted.
Harsher in Hindsight: Two interesting examples: In the fictional setting, the phone switchboard jams with calls from terrified viewers. This happened in real life as the programme was airing. Secondly, at one point Parkinson chides a distraught mother for allowing her children to watch a TV show after the nine o' clock watershed. The show creators would end up using that very point as part of their defense against subsequent criticism.
Nightmare Fuel - Pretty much the whole thing, but particularly Pipes' few onscreen appearances either subliminally, or stalking the cast everywhere they go.
Nightmare Retardant: Subverted. In the fictional setting, Craig Charles' role is to provide light relief to all the creepiness. It doesn't quite work out.
Paranoia Fuel: An especially dark version of this, as viewers who thought it was real would have been led to think they might be letting a malevolent ghost into their home via their TV set.