Two beloved cartoon veterans have passed away, according to The Associated Press. Actress Norma MacMillan — best known for supplying the voices of Gumby and Casper the Friendly Ghost — has died at 79 of cardiac arrest. She is survived by her producer-husband Thor Arngrim and children Stefan and Alison Arngrim, who played Nellie Oleson on Little House on the Prairie. And animator William Hanna, who co-created such classics as The Flintstones, The Jetsons and Scooby Doo along with partner Joseph Barbera, has died at 90.