Teryl Rothery, Peter Williams, and Tom McBeath all appeared on Stargate SG1
The album cover for "The Churchyard with Gideon Jeffries" is an homage to an actual record: John Mayall's Bluesbreakers with Eric CLapton, aka the "Beano" album because on the Mayall cover Clapton - second from left - is pictured reading a Beano comic book. The 2nd Churchyard band member from the left (Gideon Jeffries, perhaps) on their album cover is pictured reading a "Beerso" comic. This album also turns up for sale later this season at Mason's yard sale in Last Call.
George orders, for breakfast, a Jane Mansfield. That is described as a blueberry muffin, but only the muffin top. In 1967 the sex symbol actress Mansfield died when her car ran into the back end of a large truck; the tail of the truck peeled the top off of Jane's car. It was popularly believed Mansfield was decapitated.
Addendum: When George's Jane Mansfield is delivered it is two muffin tops, each with a central nipple-looking blueberry. Jane Mansfield was known for her large breasts, as well as popularly assumed to have been decapitated in a car crash. It is possible the writers were thinking decapitation but the prop folks were thinking breasts.
Mason is tasked with reaping Gideon Jefferies in this episode. Mandy Patinkin (Rube) was previously featured on Criminal Minds, playing a character named, Gideon.