Neil Patrick Harris, who is an accomplished amateur magician, performed the card tricks of the Toymaker himself.
Donna is surprised that she wasn't the first redhead to travel in the TARDIS, however Melanie Bush was not the first, either. That distinction belongs to Tegan Jovanka (Janet Fielding), primarily a companion of the Fifth Doctor but introduced in Logopolis: Part One (1981), the final story of the Fourth Doctor.
This episode marks the return of the Celestial Toymaker for the first time in fifty-seven years. There were a few attempts to bring him back before this episode. His creator, Brian Hayles, pitched an outline called 'The Eyes of Nemesis' in 1975, which would've pitted The Fourth Doctor against The Toymaker. The outline was rejected. He came close to returning in 1986 in an episode called 'The Nightmare Fair', which would've pitted him against The Sixth Doctor. However, the episode was canceled when Doctor Who (1963) was put on an 18-month hiatus before filming began; the proposed story was adapted into a novel by Target Books in 1989, and an audio drama by Big Finish Productions in 2009. The third attempt to bring him back was in the Children in Need special Doctor Who: Dimensions in Time (1993), where he was the main villain in an early draft of the script. However, his original actor Michael Gough declined to return, so he was replaced by the Rani, played by Kate O'Mara.
Mel reveals she only recently got back to Earth. So she doesn't have a family, job or home to go back to anymore. Books would later reveal this partly the Doctor's fault. The Seventh Doctor psychically compelled Mel to leave the TARDIS, having noticed Fenric's involvement with Ace time traveling; he only did it to protect Mel.
John Mackay had already played John Logie Baird for Russell T. Davies in his ITV drama Nolly (2023). It was whilst writing the drama that Davies learned of the genuine Stooky Bill dummy and his part in the inventor's early television trials at 22 Frith Street, London.