Issue: #310
Last valuation update: 2026-10-22
Story 1: "When Krypto was Superboy's Master!"Synopsis: Superboy and Krypto have their minds switched.Story 2: "The Doom of the Super-Heroes!"Synopsis: The Legion confronts a masked man looting Metropolis, who turns out to be deadly, killing the Legionnaires one by one.
First appearances: Mask Man
Creators: George Papp, George Klein, Curt Swan, Joe Letterese, John Forte, George Kashdan, Mort Weisinger, Edmond Hamilton
Characters: Superman, Mr. Mxyzptlk, Bouncing Boy, Brainiac 5, Chameleon Boy, Colossal Boy, Cosmic Boy, Krypto, Sun Boy, Saturn Girl, Ultra Boy, Invisible Kid, Shrinking Violet, Lightning Lass, Mask Man, Lana Lang, Mon-El, Lewis Lang