John Winchester and Zachariah’s returns could be connected to a previously teased disclosure about Supernatural’s 300th episode.
The circumstances of his appearance in the 300th episode remain a mystery for now.
The 300th installment of the horror series is already set to include Jeffrey Dean Morgan, which indicates that Dean and Sam’s dearly departed dad, John, will likely make his long-awaited return to the series, although nothing is ever certain in the Supernatural universe.