I don't know the reference on S.S. but I do know the letter people pretty well.
The Letter People were cool characters used in Kindergarten to teach the sounds. Our class had vinyl inflatable characters that came to the room as we learned the sounds of each letter. Mr M came first, then Mr T, then Mr H.
Let me distinguish between old letter people and new letter people. The new ones frankly stink. What you might see currently produced by whatever company, has been politically corrected beyond recognition.
The REAL traditional letter people were highly imaginative fantasy characters. For instance, (no offense Byron) Mr C was made of Cotton Candy. Mr D made of Delicious Doughnuts. Mr T had tall teeth. My favorite was Mr H who had Horrible Hair, but I liked any of the guys made of food.
The new Mr D is a "dynamic dancer. " and Mr H has been turned into Happy Hair, or something much "nicer." Also, while the vowels were female and the consonants were male, (Miss E for example was for Exercise) it was decided that there should be an equal amount of females to males, and the feminine letters became Ms instead of Miss.
The letter people made out of food no longer exist. Cotton Candy and Doughnuts and Gooey Gum are not good for you, and so those letter people were dulled down into something else.
The good news is you can still find old letter people stuff on ebay. The new liberal sanitized Letter People have a website called
www.letterpeople.com but you won't appreciate how gosh darn cool the letter people actually are if you go there. Somewhere there's a fan forum of the old letter people and I would look for that instead. I might hunt it up for you if I get a chance today.