There were two "The Promised Playhouse" episodes. This one here from 1955 which is the original and a flashback episode from 1959 called "The Promised Playhouse Flashback" In the non flashback scenes from 1959 Billy Gray does look a bit older. He would have been 21 then and in the flashbacks he was 17.
This is really a response to the other review but I didn't see any way of replying.
This is really a response to the other review but I didn't see any way of replying.