It still wouldn't have come up if I hadn't run across a great mental_floss page, "Way More Than You Ever Wanted to Know about Animaniacs", by Rob Lammle. He scored at least one long email from show creator Tom Ruegger giving lots of back story on the show's origins, including concepts for bits and characters that fell by the wayside.
There are several embedded clips from the show, but if you can only view one, make it Rob Paulsen's live remdition of "Yakko's World" with live symphonic accompaniment. Freaking wonderful. (It still doesn't tell me how he gets two lines out of a single breath where I can only do one, though. Frustrating.)
Oh, and I suppose if you've never seen the show, you really should get a taste for why it was almost as big a hit with adults as it was with kids. To that end, check out "The Ultimate Innuendos" clip fest.
Animation is thriving: plenty of shows geared toward adults air on the Fox network and cable, while kids, of course, have a smorgasbord of choices all their own. I don't know of any animated series right now that appeals to both, though, and that's a pity. Animaniacs, its spiritual ancestor The Bullwinkle Show, and Foster's Home for Imaginary Friends form a select pantheon of smart made-for-TV cartoons everyone can enjoy.