The Winchesters takes place well before events of Supernatural, the Supernatural universe makes room for time travel.
In the 1970s, it's feasible to see a few recognisable faces. Executive producers Danneel Ackles and Jensen both replied tersely.
Danneel ignored the idea that Sister Jo, the fictional figure she played, would soon return.
From what I know, her boats survived in the 2000s,Danneel explains.
Chuck replies to Jensen right away and we already know Rob Benedict is ready and willing.
There are names of people we like on the table. But if it doesn't make sense to bring a certain character back.
The audience will likely think it cool "Jensen adds. I feel that if we work
with fan favourites who played fan favourites parts, we'll be safe.