The phrase "a really famous" is correct and usable in written English.
It can be used to emphasize the level of fame of a person, place, or thing.
Example: "She is a really famous actress known for her incredible performances."
Alternatives: "a very famous" or "an extremely famous".
Homer is, after all, just a really famous cartoon.
It just would have been nice to come away with a really famous victory".
My father was friends with Wilhelmina [Cooper], a really famous model, and Eileen Ford – of the Ford modelling agency.
In a recent blog for the Huffington Post, Winters laid out some golden rules for collaborating with dead people, beginning with: "Pick a really famous dead person" and "pick a really famous book".
The 9.30 was round the back of the theatre where Lincoln was shot and it's a really famous gig venue which isn't there anymore, sadly.
A really famous writer, Alison Lurie once wrote, must seldom meet anybody who isn't aware they are meeting a famous writer.
He then kept them up on a relative shoe-string and, despite losing his best player, continues to employ an occasionally suicidal but refreshingly bold high line that threatens to make a club only really famous for Spain's coldest ground worth watching, especially against the primera's peaks.
Dannii is a pop singer who was never really famous for being a pop singer.
I read (and re-read) a lot of George Orwell's essays about when he was in Burma — you know, "Shooting an Elephant" is the really famous one, all of those.
A socialite here, a stylist there, and not one really famous person to suck the air out of the room.
Seeing bands play before they are really famous is a great way to actually get to know and talk with the band members personally - who knows, if you wanted to get into playing guitar or bass, they might be able to give you a few pointers!
