When Castiel has the demon knife hidden behind his back, the blade is a shiny chrome instead of the usual flat metal tone.
Sam and Dean go to the conjurarium to talk to the owner about the finger buzzer that electrocute's. The owner welcomes them and you briefly see the cashier counter made of glass with wood around it. Later in the scene Dean grabs a rubber chicken and uses the electric finger buzzer to melt the rubber chicken. You can clearly see he put it on some sort of stainless steel stove top not the glass with wood counter earlier.
When Sam and Dean figure out that all the strange phenomena are happening within a two-mile radius, Dean asks "Our motel isn't in that circle by any chance?" Sam replies "Yeah, why?" as if nothing odd has happened in the hotel room. But they already tested the buzzer on the ham in their motel room, which cooked, so Sam shouldn't be surprised that the motel is within the circle.