Mr. Spock, Star Trek 'The Menagerie, Part One'
Seska, Star Trek: Voyager 'Worst Case Scenario'
Mr. Magoo was also pre-Gilligan's Island. Backus had been voicing the animated nearsighted millionaire since 1949.
Should have been simple enough. Helium is non-flammable, while hydrogen burns like a sonofabitch.
Backus also played Hubert Updike III...
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