Bernstein, Swan and Kaye have Superman intentionally regress to being a baby in Action 284 (Jan. 62).
The story opens as Clark Kent reports on a phony medium. But he is surprised when a hand leaves a ghostly message for him.
Because of this message, which the reader does not see, Superman uses some red kryptonite to revert to being a baby. He retains his adult intelligence and speech, though. A few pages are spent as he continues to act as Superman, having to prove that he really is who he claims to be.
Eventually we discover that Mon-El sent the message, warning Superman about a gap opening in the Phantom Zone, which gets a long explanation/introduction in this story. Jax-Ur and Professor Vakox appear. Jax-Ur had been introduced in the pages of Adventure Comics a few months earlier, while this is the first appearance of Vakox, as well as the first time the Phantom Zone has been shown in Superman’s time period, as opposed to Superboy’s.
Superman had to reduce to infant size in order to penetrate the Zone through the gap. With the help of Supergirl and Krypto, they seal it.
Supergirl’s red kryptonite transformations continue, in this Siegel and Mooney tale.
Linda winds up with two heads, but spends her time at a carnival, where she passes as one of the freaks.
After a brief red kryptonite induced hallucination, in which she gains death-vision, Supergirl undergoes her third and final transformation, into a mermaid. That has its advantages, as she heads down to Atlantis to spend time with Jerro. This story also introduces Lenora, Lori Lemaris’s sister, who is in love with Jerro, although he has no interest in her.
When the mermaid effect passes, Supergirl is surprised to discover that her immunity to kryptonite has also vanished. Superman explains that it was all part of one of Mr. Mxyzptlk’s spells, which faded when he went back to his home dimension.
But more importantly, Superman informs her that he is finally ready to reveal her existence to the world.
The story concludes next issue.