Cleo never spoke but her wise-cracking thoughts could be heard loud and clear (voice of Mary Jane Croft). Only the audience heard the dog's thoughts; Sock was clueless as to what was on the dog's mind. Sock won Cleo (who was six months old at the time) in a poker game while stationed as a Corporal in Korea.

Her is a list of episodes focusing on Cleo's life and antics:

• On episode No. 5 "Sock vs. Crutcher" Cleo is sent to the pound - charged with snapping at someone and Socks seeks legal council to free his floppy-eared hound dog.
• On episode No. 13 "An Adventure of Sock" we learn via flashbacks how Sock and Cleo first met.
• On episode No. 22 "Sock the Escort" Cleo becomes infatuated with the pet Chihuahua of Sock's recent acquaintance.
• On episode No. 50 "How Sock Meet Rollo" Cleo retells the story of just who saved who while Sock and his boyhood friend, Hex Hexley served in the Marines.
• On episode No. 65 "The Late Husband" Cleo is smitten with a handsome French poodle owned by an actress recently moved into the trailer court.
• On episode No. 80 "The Runaway Dog" Sock hides Cleo when he discovers an influential home buyer named Mr. Quimby hates dogs.
• On episode 93 "Cleo, Secret Dog" soon to be grandfather Mayor Peoples tries to get rid of Cleo when he thinks that the dog's barking will annoy Sock and Mandy's new baby when it arrives.

TRIVIA NOTE: Originally purchased for the sum of eighty four dollars, Cleo (Bernadette) died of a heart attack at the age of 12. Her ashes rest in a tiny bronze urn in the home of her trainer, Frank Inn.

Cleo made appearances on THE PERRY COMO SHOW (voice courtesy of Mary Jan Croft) and with Jackie Cooper for the March of Dimes.

In 1958, Cleo was a winner of a PATSY (Picture Animals Top Star of the Year) Award.

Cleo also appeared in "Little Golden Book #287 CLEO" (Simon & Schuster, 1957) written by Irwin Shapiro, photos by Durward B. Graybill that featured all full-color photos from the show.

Cleo is also the name of a purple female French Poodle on the PBS kids cartoon series CLIFFORD THE BIG RED DOG.

In 1988, a Hush Puppies shoe ad entitled "Ventilated Hush Puppies" paid homage to the Marilyn Monroe film The Seven Year Itch (1955) when a sad-eyed Basset hound's droopy ears flew up when the whoosh of a subway below sent the dog's ears skyward. The 15-second commercial spot was created by Fallon McElligott agency. The dog's name was Jason.