"The Borrowed Brain!"
Supergirl helps out a young man who received a head injury while saving one of her friends.
With assistance from a Kandorian scientist, she saves his life, but inadvertently gives him super-powers. Which he uses to further his criminal ways.
"The Rock of Revenge"
Zatanna is stranded in the stone which held Excalibur, and only a descendant of Arthur Pendragon can free her.