Looking at his extensive filmography, I'm ashamed to admit I was unfamiliar with Alan Cumming's award-winning work. When he was announced as Mr. Ring-a-Ding for episode two of this season of Doctor Who, I filed the information away in the back of my head until I watched "Lux". I soon discovered that he had rightfully earned his legend status.
Where have we seen this actor before?
Alan Cumming is best known for The Anniversary Party, a movie he co-wrote and co-directed, X2: X-Men United, and the 1995 James Bond movie GoldenEye as well as many other roles, especially voice acting ones. I realized I'd seen him in the 1996 version of Emma. Doctor Who fans might remember him more recently from the 2018 episode "The Witchfinders" as King James.
What made his performance in "Lux" so remarkable?
As someone who grew up on classic Looney Tunes (and some even older stuff), the first time Mr. Ring-a-Ding spoke, I immediately felt the accuracy of his voice quality, cadence, and singing style. It was like I was watching an old Merrie Melodies cartoon. Throughout the episode, he displayed the whole gambit of sadness, cartoony joy, eager showmanship, and downright threatening villainy with the magical voice acting of Alan Cumming.
His catchphrase "Don't make me laugh!" slowly turned from a character quirk to a menacing warning, and I found myself on edge to see what would happen if he really did laugh. (The reveal that followed was absolutely unexpected!)
Do I see a future in Doctor Who for this actor?
Alan Cumming has definitely shown a fantastic acting range in his two episodes of Doctor Who, so I certainly believe they could ask him back to play someone else. It would just need to be another character as iconic as he is.