Guest Stars Bumper Robinson voices Falcon Laura Bailey voices Black Widow David Kaye voices Jarvis Liam O'Brien voices Red Skull Jim Meskimen voices Ultron Chi McBride voices Nick Fury Isaac C. Singleton, Jr. voices Thanos Troy Baker voices Howard Stark Clancy Brown voices Uatu 'The Watcher' David Kaye voices Computer Roger Craig Smith voices Grim Reaper