WARNING: The following contains spoilers for Season 15, Episode 7 of Supernatural, "Last Call."
As you might expect for a beloved, long-running series drawing to a close, Season 15 of Supernatural has been putting out a veritable smorgasbord of callbacks in each new episode, from character cameos to jokes about how Sam and Dean have aged over the past decade. It's clear that the show is knowingly reveling in its own legacy -- both the good (Agents Ford and Hamill) and the bad (Leviathans, anyone?).
The latest episode, "Last Call," features two unmissable references, both of which can be traced back to one particular episode from Season 4, "Yellow Fever."
In "Last Call," Dean heads off to work a case alone that he hopes has some kind of connection to Chuck/God. His investigation takes him to a rural Texas bar that just so happens to be owned by an old buddy of his, Lee Webb, played by Angel alum Christian Kane. As former hunter, Lee used to go on jobs with Dean and his father, John, before retiring from "the life" for good, before Sam entered the picture. The two haven't seen each other since, and soon start catching up over round after round of drinks.
It's during one of these conversations that Dean tells Lee a story about coming down with ghost sickness, which made him so jittery, he ended up screaming at the sight of a cat. That moment occurs in "Yellow Fever" when Sam and Dean are poking around an abandoned wood mill. The sickness Dean contracts makes its victim become more and more consumed by paranoia until their escalating heart rate kills them. When Sam tentatively opens up a locker and finds the stray animal inside of it, Dean lets out an uncontrollable, high-pitched squeal in shock. It's a scene that's helped the episode go down as one of the show's funniest ever.
If that wasn't enough, when Lee later persuades Dean to step up on stage with him for some impromptu musical stylings, he tells him: "C'mon. boy, you can't just sit around lip-syncing 'Eye of the Tiger' while nobody's watching." That's, of course, a callback to the other, even more fondly remembered part of "Yellow Fever," where Sam finds Dean hiding out in the backseat of the Impala, mouthing along to the Survivor song to calm his nerves. A full version of actor Jensen Ackles' performance also plays as a post-credits treat for viewers, with Ackles even climbing onto the hood of the car to deliver it -- much to the delight of the laughing members of the crew.
What's especially fun about Lee's line in "Last Call" is that, in order for it to make sense, you have to assume that lip-syncing to 'Eye of the Tiger' was far from a spur of the moment thing for Dean in "Yellow Fever." Rather, Lee must have caught him the act when the two were still hunting together for him to have known about it happening; a leap of logic that we're more than prepared to make for more Easter eggs like this one.
Airing Thursdays at 8 p.m. ET/PT on The CW, the final season of Supernatural stars Jensen Ackles, Jared Padalecki, Misha Collins and Alexander Calvert.
KEEP READING: Supernatural: 5 Characters From the Early Seasons Who Need to Return