the very first animated adventures of the Justice League of America were aired in the 60s. I never saw one of these growing up, but it would have been awesome, despite the rather lame villains they used. the intro alone is great. too bad Aquaman isn't even in the episodes though. I wonder why they didn't use Wonder Woman, since Wonder Girl was in the Teen Titans.
some people still think that Super Friends was the first version of the JLA. this is probably the best episode in the series. lots of action and an alien invader who doesn't seem silly.