Final appearance of Stuart Milligan as Adam Klaus.
When Jonathan & Joey become trapped in the old coal cellar, neither of them think to use Joey's mobile phone to call Emily for help, even though Joey has Emily's number, as she took a phone call from her earlier in the episode.
Paul McGann is the third former star of 'Doctor Who' to guest star in an episode. Colin Baker (the Sixth Doctor) was in the first episode and Peter Davison (the Fifth Doctor) appeared in the second season. McGann played the Eigth Doctor.
Sheridan Smith and Paul McGann both star in this episode, reuniting on screen from their Big Finish Doctor Who audio adventures. McGann's eighth doctor was joined by Smith's companion Lucie Miller for four series of the audiobook expanded universe.
Six actors from this episode also appeared in Lewis series: Marc Small, Sasha Behar, Doreen Mantle, Alan Davies, Stuart Milligan, and Ian McNeice.