I already mentioned this to Byron, but if Henson had done "The Letter People", here's who I think would have voiced which Letter People:
JIM--Mr. M, Mr. W, Mr. X
FRANK--Mr. D, Mr. G, Mr. K, Mr. R, Mr. T
JERRY--Mr. C, Mr. N, Mr. P, Mr. V, Mr. Z
RICHARD--Mr. F, Mr. H, Mr. J, Mr. L
DAVE--Mr. B, Mr. Q, Mr. S, Mr. Y
KATHRYN--Miss A, Miss U
KAREN--Miss E
LOUISE--Miss O
FRAN--Miss I
Nowadays, I think it would probably be:
FRANK--(see above)
JERRY--(see above)
DAVE--(see above, subtract Mr. Y)
KATHRYN--(see above)
KAREN--(see above)
LOUISE--(see above)
FRAN--(see above)
DAVID R.--Mr. F, Mr. J, Mr. W, Mr. X
KEVIN--Mr. M
ERIC--Mr. H
STEVE--Mr. Y