7. What unusual distinction is shared by all these performers? Phil Hartman, Don Knotts, Roddy McDowall, Zero Mostel, Paul Newman, John Ritter, Jimmy Stewart, Orson Welles. The final movie role of all these late stars was a voice performance in an animated film. RIP Paul Newman.
So I guess I'll have to supply it myself.
Phil Hartman: the cat Jiji in Kiki's Delivery Service (US dub), 1998
Don Knotts:the turkey Mayor Turkey Lurkey in Chicken Little, 2005
Roddy McDowall: the ant Mr. Soil in A Bug's Life, 1998
Zero Mostel: the seagull Kehaar in Watership Down, 1978
Paul Newman: the race-car Doc Hudson in Cars, 2006 (though Wikipedia says he was a narrator for the 2007 film Dale - guess that doesn't count as a "role"?)
John Ritter: the big red dog Clifford in Clifford's Really Big Movie, released 2004
Jimmy Stewart: the dog Sheriff Wylie Burp in An American Tail: Fievel Goes West, 1991
Orson Welles: the planet-eating robot Unicron in Transformers: The Movie, released 1986