Underdog's adventures usually were in the form of 4-part serials, which, in syndication, stretched across two episodes. For a period in the late 60's & early 70's, NBC would put the serials together to air them in one sitting.
The first three shorts, however, are done-in-ones that illustrate that while he is dedicated to his mission, Underdog (Wally Cox) leaves a path of destruction in his wake. Lord knows how many phone booths were destroyed when Shoeshine Boy had to change to Underdog. Anyway, those three stand-alone shorts--"Safe Waif", "March of the Monsters", and "Simon Says"--are all here, plus the debut of the Go Go Gophers ("Moon Zoom") and Commander McBragg ("Over The Falls").
We would see better from the Gophers, and McBragg got repetitive in a hurry, to the point where the joke gets lost. Underdog is back in comics, as American Mythology Press obtained a license earlier this year. The others? Not so much.
Some sources don't have "Moon Zoom" as the Gophers' 1st episode. The copyright is 1962, but they didn't debut until 4 years later. Hmmmm.