Kevin asked in a comment about the "letter people". As far as I know, they long gone. I was a bit shocked I had never heard of them given that anything on PBS in 1974 was right up my alley. The story of their 1990 shift to political correctness is worth a look, though.
Let's hand this question off to Crib Chick and Susan, both of whom see more kid TV than I do. Ladies, please advise.
All this letter talk, however, reminded me that I have never told you about the Vowel Movement Kids.
I don't know who they are or how it starts, but every day at lunch the kids start to yell, "OOOOooooooohhhhhhhhhh". It seems to have no reason other than the power of the kid who first yells and somehow makes the others yell with him. It has happened without fail for the last four or so years.
My room is directly off the cafeteria, so all the mischief of the other two lunches are heard by my students. When the corporate moan begins, I dryly ask the students to ignore it, that some children are trying to start a vowel movement.
A couple of years ago, I had some Drama kids in class who ran with the vowel movement concept. They decided to answer "OOOOOhhhh" with the rest of the vowels. It was something to hear, all those kids yelling "Aaaaaayyyyy, Eeeeeeeee, Iiiiiiii, Oooooohh, UUUuuuuuuu, Sooooome-Tiiiiiimes--YYyyyyyyyy!!!"