Quel joli personnage!

Question

Why is « Quelle une jolie caractère » not alternative please?

Accepted Answer

Bonjour Olasimbo,
'quel(s)' / 'quelle(s)' are part of what is called, in French grammar, the exclamative or interrogative adjectives according to how they are used (are they part of an interrogative sentence or of an exclamative sentence). 
Their form change depending on the gender (feminine / masculine) and on the number (singular / plural) of the noun they are referring to.
Exclamation / masculine noun : Quel hôtel = what a hotel!
Question / feminine noun : Quelle heure est-il? = what time is it?
 
They can be directly followed by a noun OR by an adjective and a noun:
Quel hôtel! = what a hotel!
Quelle merveilleuse idée! = what a splendid idea!
 
They are NEVER followed by an article as in English.
Please follow the link for further explanation:
questions-quel-quels-quelle-quelles-which-what
 
I hope this is helpful.
Bonne journée!

Answer

«Quel(le) - followed by article - un(e)» is incorrect - see the associated grammar lesson. https://progress.lawlessfrench.com/revision/grammar/how-to-express-what-a-with-quel-quelle-quels-quelles.

I looked at using «caractère» too - but it is more typically applied to temperament/personality than to appearance as was indicated here, so settled on «personnage» as better option.

In either case, caractère or personnage, the nouns are masculine, so it would be «joli» regardless of whether the drawing was of a male or female.