We think we know the song that might get stuck in your head for a bit this week, thanks to Doctor Who. This next episode, titled “Lux,” features Alan Cumming voicing the animated Mr Ring-a-Ding, and TV Insider has an exclusive sneak peek of the Doctor (Ncuti Gatwa) and Belinda (Varada Sethu) getting a look at and meeting him for the first time. In the clip, the two cautiously approach the singing character at the front of the theater. “What a fine and dandy day, and who might you be?” Mr Ring-a-Ding asks. The Doctor introduces himself and Belinda and asks who he is — then has to put a stop to Mr Ring-a-Ding singing. “You’re a cartoon,” the Time Lord says. “Don’t make me laugh,” Mr Ring-a-Ding says. “You are a living cartoon,” the Doctor says, amazed. Belinda’s confused, considering the technology for such a thing shouldn’t exist yet.