Originally Posted by theMan-Bat
That Super Powers Team: Galactic Guardians episode "The Fear" was written by Alan Burnett and aired on October 2nd, 1985. Frank Miller's Batman: The Dark Knight Returns was released on February 1986, and had been written and illustrated already by mid 1985, as Comics Journal #101, August 1985, confirms with an interview with Frank Miller that was conducted in June 1985, and showed panels with dialogue from the forthcoming mini-series.
And the episode was probably written way before that. So this doesn't really prove or disprove anything.
But I don't think he got it from there, Frank Miller just didn't have a clue and didn't bother to do some research, the same happened in "Year One".