The episode: “The Painted Hills,” ep. 510
The riff: Belted out by Tom during one of the movie’s many establishing shots in the wilderness, full of trees and a clear blue sky.
The explanation: The joke is an excerpt from the song “Seattle” by pop singer Perry Como, from his album of the same name. The actual lyrics go: “The bluest skies you’ve ever seen are in Seattle/And the hills the greenest green, in Seattle.”
Novelty factor: This is definitely not the sort of musical reference I’m going to be likely to pick up on. My iTunes library contains a grand total of zero Perry Como tracks.