When Gus and Shawn are getting ready to sit down in the stadium, there is a large stuffed raccoon in a seat behind them. You see the lady beside it pick it up so someone can sit down. The camera then cuts in closer after they sit down, and the raccoon is in the seat, and then picked up again by the lady.
On seeing a man wearing a Dunkin Donuts jacket, Gus praises the chain's coffee and mentions a location he frequents on his pharmaceutical route. In 2008, there were no Dunkin Donuts locations in California.
Just before Shawn cuts off El Diablo, tire tracks from previous takes can be seen on the grass.
The California State Fair is held in Sacramento, which is more than 350 miles away from Santa Barbara.
After Shawn and Gus find out that Louis is El Diablo, Shawn picks up Louis' helmet, the helmet has a reflection of the boom mic.
Gemcitabine and Capecitabine are chemotherapy agents used for a variety of cancers. While pancreatic cancer can be treated with these agents, they're used for colon, breast, and other gastrointestinal malignancies as well. Pancreatic cancer is much rarer than colon or breast, and it wouldn't be the first cancer one would guess given those drugs.