Dean's line: "Nazis. I hate these guys.", is an echo of the same line from Indiana Jones and the Last Crusade (1989), when Indy discovers Nazis in an Austrian castle. It's also similar to lines said by Jake in The Blues Brothers (1980): "Illinois Nazis. I hate Illinois Nazis."
Keenan Tracey ("Christoph") is the son of Ian Tracey, who portrays the hunter Lee in season 7's Adventures in Babysitting, and later this season portrays Ishim in Lily Sunder Has Some Regrets.
When Dean shoots Hitler he uses a Walther P99 instead of his usual Colt 1911. Hitler killed himself with a Walther PPK.
Adam Rose had previously portrayed Aaron Bass in Season 8 - "Everybody Hates Hitler".
Allison Paige (who played Ellie) is known for playing Bev in 'Days of Our Lives' which Jensen Ackles also starred in.