The episode: “The Brute Man,” ep. 702
The riff: Sung off-key by Mike as a blind woman plays the piano. Tom is briefly singing “O Holy Night” the same way just before him.
The explanation: This seems to be a reference to the lyrics of the Elvis Costello song “Stranger in the House,” from his debut 1977 album “My Aim is True.” As for the context…I have no idea at all. It’s possible they’re making a very literal reference because the “Brute Man” is hiding in her apartment during this time, so there’s literally a “stranger in her house.”
Novelty factor: No way in hell I knew this. I barely know any Elvis Costello.