I'm sure it's been said before, but I just rewatched the Nightcrawler episode and the one where the Xmen have to restore Juggernaut's powers to save his life. Pretty heavy themes-- no cartoon would tackle religion these days like the Nightcrawler episode did. The Juggernaut one had a great parody, as the new Juggernaut fell through a studio called "Banzai Films" where two power rangers are fighting dinosaurs. Even the music hinted at the power rangers theme. Mature themes + hilarious parody = cartoon for kids that was way ahead of its time for the early 90s.