Fans of the Fantastic Four's comic book had to be going nuts seeing Galactus make his TV debut in this 1967 episode. The quibble is the fact that while Galactus had the same skin tone as humans in the books, he was given lime green skin here (and voiced by an uncredited Ted Cassidy). Paul Frees pulls double duty, speaking for the Watcher in addition to his usual role as The Thing.
Another quibble is the absence of Thing's blind girlfriend, Alicia, as in the comics, it was she and not Sue (Jo Ann Pflug) who befriended the Silver Surfer (Vic Perrin, also uncredited), an oversight corrected in a later incarnation of the series. Considering how Hanna-Barbera wasn't able to have 100% rights to the characters, well.......!