The diner scene where Dean meets his young father John Winchester for the first time pays homage to the same scene in Back to the Future (1985) where Marty first met his young father George McFly also in the diner. The only difference is the year: 1973, not 1955.
One of the demons is named Dr. Brown, same name as Christopher Lloyd's in Back to the Future (1985).
When Dean asks young John if he knows where to get cell phone reception with his flip phone, John answers, "The USS Enterprise." The designers of the flip phone purposely made the first cell phones to mirror the communicators from the classic TV series Star Trek (1966).
In the diner scene Dean mentions that Sonny and Cher broke up, causing puzzled responses as it's two years away (1975). The fact that Ramblin' Man by Allman Brothers is playing at the same time is likely a subtle nod to the fact that Cher married Gregg Allman right after the Sonny/Cher break-up.
Dean asks Castiel if the angels got their hands on a DeLorean, one of several references to Back to the Future.