With regard to Pat Wayne playing the baby in Stagecoach...he wasn't born until September of 1939. The filming was completed in mid-late 1938, or at the very earliest, the first couple of months of 1939.
It would've been cool if it WAS him, but it couldn't have been...:(
It would indeed be 'cool'
However I thought Patrick was born on July 15th!
So we can hope, just a little!