The episode: “The Brain That Wouldn’t Die,” ep. 513
The riff: Asked quiz-style by Tom to Mike, who replies “Uhhh…Now I know why the show is called V!” This is Mike’s first episode of MST3k, and the bots are “training” him on how to riff bad movies. The Marc Singer question is part of his final exam.
The explanation: This is a two-part joke that shows the way the writers associate multiple pop culture properties at once. Mark Singer was a Canadian actor who was well-known for his starring role in the “Beastmaster” series of films. This is where the “loincloth” reference comes from. But Mike’s reply references the TV miniseries 1983 “V,” (remade in 2009) where Singer played the role of Michael Donovan, the leader of the human resistance. The second joke references both that and the “v-shape” of a loincloth, I presume.
Novelty factor: I didn’t know who Marc Singer was, although I’m aware that “Beastmaster” was a camp classic, and I’ve seen the original “V,” but not the remake.