Ian Abercrombie's last major credit was as the Headmaster in Wizards of Waverly Place, which just wrapped up a few weeks ago. This is the second time in recent memory that Disney's wrapped up one of their shows, only for one of the big stars to pass away a few weeks later. The first case was with The Emperor's New School, where the show wrapped up and Eartha Kitt passed on weeks later. It's a very odd coincidence.
As JST alluded to, he also currently leaves Star Wars: The Clone Wars without a Palpatine. He was awesome in that role.
Someone behind the scenes on SNL must REALLY love the WWE. This movie, based on the MacGyver like character played by Will Forte, features six WWE wrestling that I recognize off hand... Jericho, Big Show, MVP, Kahli, Mark Henry and Kane.