One question and one comment regarding this cover: First, you don't see a lot of scratchboard on comics covers, so points for that.
Second--just where are Green Arrow and Aquaman's legs, exactly? Bad Chua!
The Story: An Untold Tale from the JLA Casebook: "Skyjack at 22,300 Miles!" by Martin Pasko, Dick Dillin, and Frank McLaughlin. Set during the events of JLA #s 78 and 79, we have Hawkman explaining to Flash how JLAers are supposed to arrive at their new satellite HQ, via rooftop teleportation tubes.
At the same time, inside the building Flash and Hawkman are meeting on, S.T.A.R. Labs, your typical comic book scientist is working on something that goes horribly wrong, and a moon rock is cracked open, spilling a weird purple creature out of it, which attacks the scientist and jumps out the window.
As the two JLAers beam themselves up, the creature converts itself into a gas-like shape and sneaks into the tube, as well. Flash and Hawkman notice this, but its too late to stop it!
When they arrive, they have been morphed into three hybrid creatures, one with Flash's head, Hawkman's body, and the creature's legs, the others having all the opposite attributes! They attack the bewildered JLAers and quickly knock them out.
But instead of escaping, the creatures use the JLA library to do some sort of research, and then they start trying to pull the satellite out of its orbit and put it on a new trajectory.
Turns out the creature--named a Dharlu--was a mother, and it was following its instinct to return "home" to give birth. The JLA of course stops it, but it has a peculiarly weird ending, where the JLA traps the Dharlu inside the JLA computer, freezing it into a sort of suspended animation, where it will stay forever!
Roll Call: Superman, Aquaman, Flash, Green Lantern, Green Arrow, Atom, Hawkman, Black Canary
Notable Moments: It seems kinda cruel to keep this creature trapped in a sort of living death inside your computer. I mean, jeez.
According to the Statement of Ownership, Justice League of America was at this time selling about 173,000 copies per month, out of 412,000 printed! Wow, that's a pretty poor "sell-through" for what I always thought was one of DC's heavy-hitters.
The book had just been "promoted" to monthly status, for the first time in its fifteen year history, so obviously DC was ok with these numbers.