I also remember things like the old classic Klasky Csupo Nicktoons or Hanna-Barbara's Cartoon Network era stuff. One of my fav things to do now is go back and reread history and the behind the scenes strides of these companies and creators, those old feuds that influenced stylistic changes and choices, purchasing decisions and contracts, answering the question, "What ever happened to___?"
Another one that still gets to me, despite how obnoxious it is, The Grim Adventures of Billy and Mandy. Old love, Mandy the feckin' heartbreaker. ❤