The basis for this comes from two incidents pertaining to Characters from Fantasy RPGs I had rolled up.
The first incident occurred when I described a Fighter I had once played: 18 Strength, 17 Charisma - gone too soon and much missed. The chap I was talking to took this in and said (as well as I remember it) "So, he would just flex his muscles at people and they'd come running?"
The second, when I was in the process of putting together a Dwarven Cleric. Charisma ended up being one of the lower stats; only 5 or thereabouts. One of my fellow players, in sporting mood, looked at this and described my character as "short, hairy, and grunting at people". Now it is true that Charisma does have some bearing on social interaction - but my conception had been of a hellfire preacher; certainly unlikable and certainly not terribly sociable - but not inarticulate. However much my friend's interpretation rankled, it didn't stick as our campaign progressed (slowly).
Now, discussion and interpretations of Ability Scores is nothing new (here and here, for instance, are two posts on Wisdom). But Charisma may be impinged on by other scores - hence, my glorious muscle-bound knight. Emphasis on 'may'; a steely-thewed warrior might also be terribly articulate; who can tell quite what his body looks like under all that plate armour?
Anyway, here are some thoughts on what a character might look like (this is hardly authoritative, or even notably thorough) as I 'ring the changes' on a Charisma and other Ability Scores. My point of reference, as ever, is The 52 Pages - but this isn't so very unfamiliar to other systems.
STR 18; CHA 18 - You are gigantic, but remarkably comforting to have around.
DEX 18 CHA 18 - You are swift and graceful as a swan. Everyone else loves swans.
INT 18 CHA 18 - You always have a solution - and, what is more, you can explain it in all its complexity!
WIS 18 CHA 18 - You are terribly considerate of others and notice when things are wrong.
CON 18 CHA 18 - You epitomize that moment when the Protagonist sees the Love Interest after hard work or exercise with a 'healthy glow' about them.
STR 3 CHA 18 - You are weak as a newborn kitten. Everyone else loves kittens.
DEX 3 CHA 18 - You are clumsy as a young fawn. Everyone else loves fawns.
INT 3 CHA 18 - You are, or could pass for, Bertie Wooster.
WIS 3 CHA 18 - You are frequently oblivious to your surroundings, but when other people get your attention, they find you pleasantry amenable. [This works the 'willpower' part of Wisdom in quite nicely.]
CON 3 CHA 18 - You are absolutely lovely, but probably dying of tuberculosis. The Romantic Poet of the party.
STR 18 CHA 3 - You are over-muscled to the point of parody. Even in a world of magic and mystery, it looks unnatural and unnerving.
DEX 18 CHA 3 - You move like a snake, you strike like a snake. Everyone else hates snakes.
INT 18 CHA 3 - You possess Mr. Spock levels of pitiless, pragmatic logic. [Neal Stephenson's Anathem has a series of 'Iconographies', largely on this basis in Chapter I]
WIS 18 CHA 3 - You are much like T.H. White's Sir Galahad in The Once and Future King; far too good to be merely polite. [Ch. XXXII of The Ill-Made Knight]
CON 18 CHA 3 - When everyone else has collapsed from exhaustion, injury or fatigue, you'll be standing upright and firm, ready to push on. This is useful, but hardly appealing.
(Not quite as happy with this last lot.)
STR 3 CHA 3 - "We've only been going ten minutes!"
DEX 3 CHA 3 - "Which blockhead gave you a crossbow?"
INT 3 CHA 3 - "How many times do I have to tell you...."
WIS 3 CHA 3 - "Pay attention! That ambush almost cost us our wizard!"
CON 3 CHA 3 - "Come on, that's just a flesh wound!"
Again, these are all open to interpretation. But it's all part of the interplay of Ability Scores and Role-Playing, and these are a few options.