fictional character vs Walter Mitty

fictional character and Walter Mitty both are nouns.

Word	Noun	Adjective	Verb	Adverb
fictional character	Yes	No	No	No
Walter Mitty	Yes	No	No	No

fictional character (noun)	Walter Mitty (noun)
an imaginary person represented in a work of fiction (play or film or story)	fictional character created by James Thurber who daydreams about his adventures and triumphs