Here is a "blurb" about one of the earliest CBS shows:
One of the first Saturday morning shows to grace the television screen was also one of the most creative. The delightful Mr. I. Magination starred Paul Tripp, author of the children's book Tubby the Tuba. Each week, Tripp would dress in his trademark engineer’s overalls and take the audience on a virtual train ride.
Special effects hardly existed in the 50's, but Mr. I. Magination didn't need any. As the magical locomotive toured around Ambitionville, Inventorsville, Sea-Port-City, and "I Wish I Were" Town, Tripp and his actors each played several characters per show, thereby helping to create convincing imaginary scenarios.
Despite the show's immense popularity, CBS cancelled Mr. Tripp’s ticket and told everyone to disembark after one year. Angered by this move, children and parents protested until the network brought the show back.
Its return was hailed by CBS with this New York Times ad:
“Returning today by popular demand! Mr. I. Magination…because it’s like no other program in the world…because it’s full of charm and humor and fantasy…because watching it is always a truly delightful experience…children of all ages have demanded the return of Mr. I. Magination. So Paul Tripp is back…conducting tours through space and time, fiction and history…turning young friends into their favorite heroes.”
Though Mr. I. Magination finally came to a permanant halt in 1952, its emphasis on imagination set the standard for many children's television shows to come.