The Adventures of Superman Radio Serial - May-June 1943
The scarcity of episodes from this era is a genuine shame, if owing almost entirely to the presence of The Meteor From Krypton among 1943’s catalog. Although Jerry Siegel had intended to introduce what we know today as Kryptonite in an earlier story - the unpublished K-Metal From Krypton, editorially kiboshed owing to Siegel additionally upsetting the apple cart by having Lois permanently learn Superman’s dual identity - it’s here, on the radio show, that Superman’s fatal weakness debuts, and the name of Superman’s home planet becomes first known to Superman’s supporting cast.
The episodes from this missing two-month period include:
"Master of the Dream World"
"The Ghost Squadron"
"The Meteor from Krypton"