"The Big Forget"
Superman can't seem to remember his civilian identity. He thinks he has it figured out, but when he sees Clark Kent; he knows he has to come up with a new identity until he finds out what his real one is.
Note: This story runs through Action Comics (1938) #371-372 and #374-375.
"The Woman Who Hated Supergirl"
When Supergirl helps a professor examine a rare nebula, it causes nothing but problems.