I don't know about creating all the letters from it. But I remember someone praising R for having most of the elements needed: stem, bowl, and tail.

Obviously, he was speaking figuratively. There is no such letter.

The obscure fellow typophile might not have meant one particular letter which all the others stemming from. I guess, he was rather talking about “when you see one letter you can reconstruct the whole alphabet”.
I’ve never tried myself but it might be some kind of typophile sportsmanship to spot just one (or five or seven …) letters af a typeface on any artefact – and go designing the whole alphabet.

Could be a nice competitive exercise, actually.

I found the quote I remembered, it’s from H&FJ:
http://www.typography.com/ask/faq.php?faqID=66#Faq_66

What a lovely quote! –and a much better way to put it –that "the R synopsizes the rest of the alphabet in a single character" --exactly what i was searching for. Thank you kindly!

Otherwise there's always Jack Usine's Pananatomic Ligature.
http://www.usine.name/index.php?/typo/ligature-pananatomique/
:-)

Actually, Jonathan and Tobias are secretly talking about this:
http://www.themicrofoundry.com/ss_uniglyph1.html

hhp

The “Pananatomic ligature” is an intersting idea. But, not so successfully executed, I fear. He is frankensteining capital and minuscule parts, which I don’t understand why.