This was an amazing episode. From the beginning scene to the impressive finale, this episode had almost everything that wowed me about this show. I was initiatially shocked at the premise of having the Legion actually killing one of the Superfriends and threatening to do it to all of them. After all the clumsy censorship that plagued other action cartoons of the era, that was what really drew me to this episode as more than just another \\\"challenge of the super-friends\\\" ep.
Of course, as with this show, it was detracted from heavily by its limited animation and flagrant abuse of internal consistency. But, just for this episode, I was able to ignore all that and enjoy it.
This was my favorite episode as a kid. It seemed to me that the end had really come and that the Legion of Doom had actually won. There I was sitting on my couch when I see a figure in a radiation suit pick up the crystal with tongs and say " I have it". I knew at that moment that the good guys still had a chance to win. When they did return from the dark side of the moon, if I remember correctly, I was the happiest kid you would ever meet. This is the best episode of the series and I wish they would release it on DVD.