Sam and Castiel took the names of Tom Scholz and Bradley Delp of the band Boston as their FBI cover.
This episode was filmed in the same location as Once Upon a Time (2011)'s Storybrooke. Noteably Regina's house in Steveston.
In addition to taking the rock aliases of Tom Scholtz and Bradley Delp from the band Boston, the name, "Peace of Mind" is after a Boston song from their first album.
In the opening scene, the marquee for the movie theater has a sign for a $2 showing of Scooby Doo, a possible nod to ScoobyNatural (2018).
In Harrington's shop, note the pale green milkshake machines. First: that 'Jade Green' hue was THE kitchen color of the 1950s. Second: the Hamilton Beach 40DM triple spindle commercial immersion blender was the workhorse of almost every shakeshop. A slightly updated HMD400 is still the standard milkshake machine.