What people forget about Challenge of the Super Friends is that it was originally a 1 hour show. The first half continued the team adventures from the previous year, and the second half was the Justice League vs. the Legion of Doom, with the Wonder Twins conveinently in absentia (though they'd encounter some of the Legion members, including Lex Luthor, in later seasons).
Just in time for Halloween, we offer up "Terror From The Phantom Zone". Three Kryptonian outlaws, long banished to the Phantom Zone, somehow find their way to Earth, bringing with them some Red Kryptonite, which is the first time that variation on the Kryptonite was used in the franchise, and would be used again a couple more times in succeeding seasons.
Edit, 7/26/18: Dailymotion deleted the video. Soon as we find another copy, we'll bring it back.
In some ways, this would be a precursor to Superman battling three different Kryptonian foes in "Superman 2", three years later, and that was actually a better story.....!