The Letter People is a children's literacy program and the television series based on that program. The term also refers to the various characters depicted in the program and television show.
First produced in 1972, The Letter People was an Edutainment Showcreated by the St. Louis PBS station KETC and was based on a phonics program for children that featured a cast of anthropomorphic letters. Using primitive puppets and simplistic backdrops, interspersed with Non Sequitur animated sequences, each episode would either introduce a Letter Boy or Letter Girl, or explore a new phonetic principle, such as "silent e" or the "ing" sound. Every Letter Person had his or her own special sound, demonstrated by their outfits and Mad Libs Catch Phrases. Living alongside the Letter People were the other denizens of Letter People Land, ranging from the Purple Peekaboo Palooklas to Game Show Host Monty Swell, who hosted the Show Within a Show, "The Catching Game", in which contestants sounded out words and won prizes that relate to them.
Soon after its premiere, the show began to gain popularity and spread to other PBS stations via syndication. Its popularity largely grew from the fact that, despite being based on the rather mundane topic of phonics, all of the characters have rather distinct personalities (Large Ham: Mister G, Jerk with a Heart of Gold: Miss O, The Cape: Mister S). Also, even with the show's simplistic nature, a number of the Letter People went through a good deal of Character Development and found themselves involved in a number of wacky hijinks. And according to The Other Wiki, the show has aired almost constantly since its premiere.
The complete series is now available on YouTube.