Based on the 1960's primetime CBS sitcom My Favorite Martian, this cartoon changed the format around slightly by adding extra characters. Newspaper reporter Tim O'Hara and "Uncle Martin" were now joined by Tim's niece Katy, another antennae-headed Martian named Andromeda, and shaggy pet alien-dog Oakie Doakie.
The O'Haras protected the crash-landed aliens' identity by pretending that they were Katy's Uncle Martin and his nephew Andy. The sudden influx of "distant" relatives living with Tim and Katy sparked suspicion with neighboring Detective Bill Brennan and his son Brad, who routinely tried to uncover the truth about their mysterious neighbors. Another holdover from the sitcom was Lorelei Brown, Tim's dizzy landlady, who had a crush on Uncle Martin.
None of the actors from the original series provided character voices for My Favorite Martians. Replacing Ray Walston as Uncle Martin was another sixties sci-fi TV star, Jonathan Harris (Dr. Smith from Lost In Space). Playing both Mrs. Brown and Katy O'Hara was Jane Webb, who was also the voice of Filmation's Sabrina the Teenage Witch.