While searching the barn, the Thunderbolt makes reference to "Biff Tannen-level manure". In each of the Back to the Future films a member of the Tannen family ends up in manure. In the first two films Biff Tannen has an accident where a truckload of manure gets dumped on him.
The Blue Valley theater is showing a Nathaniel Dusk film. Nathaniel Dusk was a PI in two four-issue DC mini-series in the 80s. The character also exists in the comics as the main character in the the Watchmen 'Doomsday Clock' series, where he's played by actor Carver Coleman, who Dr. Manhattan met several times during Coleman's career.
At Etter Produce Farm, Thunderbolt says "Biff Tannen level manure". Biff Tannen is the villain of Back to the Future. Back in 1955, at the climax of the skateboard chase in the town square, Biff drives into a truck full of manure which fills his open top vehicle.