The nominal cover artist for the original Justice League series was the interior artist Mike Sekowsky. However, there were times when Mike would be unable to draw the covers when Julius Schwartz needed them. In those cases Julie would turn to the cover inker Murphy Anderson, a talented penciller in his own right, to supply the entire cover.
When Murphy and Julie collaborated they, like a lot of editor/artist teams at the time, would create a cover before creating the story. And when stumped for ideas they’d raid an old stack of pulp magazines for ideas (which ironically contained storied edited by Mort Weisinger before he came to DC Comics) or, self-referenced their own ideas from old DC science fiction comic covers which Murphy had done for Julie.
These are the most famous examples of their self-referencing:
Mystery In Space #9 Versus JLA #4:
Sensation Comics #109 Versus JLA #10:
Mystery In Space #17 Versus JLA #19:
Mystery In Space #19 Versus JLA #22:
[Cover Credit: GCD]