2. The DCAU Included An R-Rated Series Full Of Violence And Profanity
The DCAU frequently pushed the boundaries of what they could get away with on what was still ostensibly a set of kids' shows (Roxy Rocket was pretty much wall-to-wall innuendo, after all). The movie Return Of The Joker was intense enough that it had to have scenes of violence and blood removed to even receive a PG-13 certificate (the first animated Batman movie to get above a PG).
There was, however, briefly a DCAU series that pushed things further. Much, much further in fact. In 2000, Lobo: The Webseries brought foul language, sexual content and over-the-top violence to the DCAU for the first (and last) time.
In the 1990s DC Comics's space biker intergalactic bounty hunter had become something of a fan favourite when transformed from a tough guy villain into a loud mouth obnoxious ultra-violent antihero. So of course DC wanted him brought into the Animated Universe, making his first appearance early in Superman: The Animated Series in the 1996 two-parter The Main Man.
There were bigger plans beyond that, however, as DC considered a full spin-off for the character. Ultimately, it was hard to turn a character known for being extreme in all senses into a family-friendly cartoon, so the project was reconfigured as a webseries of 14 short flash animations with the freedom to be as crude and violent as they liked.
The series was never given any form of home media release and the website on which it could be found, loboonline.com, has been discontinued, so it can be easy to forget that for a brief moment the DCAU pushed well outside its usual PG boundaries.