Quotes / Only Known by Their Nickname

Karrde: We haven't yet been able to decipher the message, but it definitely contained Thrawn's name. His full name, not just the core name 'Thrawn.'
Han Solo: I didn't even know he had more name.
Karrde: Most people don't.

"We're the thin/fat gay married Anglican Marines. Why would we need names as well?"

"My nickname's Boss! Even the author doesn't know my real name!"
Boss, Shin Mazinger

Spiros: He knows my name. But my name is not my name. And you? To them, you are only "The Greek."
The Greek: And, of course...I'm not even Greek.

"He asked me to stop calling myself Blackfish. Said it was an old joke, and never funny to begin with. I told him people have been calling me Blackfish for so long, they don't remember my real name."
Brynden Tully, Game of Thrones

"The true name of Cappadocius is lost to the winds of history, known only to the vampire himself and written nowhere. As the gradual mingling of cultures in the world progressed, Cappadocius chose for himself a name that revealed his origin and nothing else, and this he gave to Caine and his childer when they selected Cappadocius for the Embrace. "Of Cappadocia" is all the world knows of this enigmatic Cainite, and it may be all it ever knows."
Vampire: The Masquerade - Clanbook: Cappadocian

"My name, my real name, that is not the point. The name I chose is the Doctor. The name you choose it's like, it's like a promise you make. He's the one who broke the promise."
The Eleventh Doctor regarding the "War Doctor", "The Name of the Doctor"

''"The Big Dipper! I thought your parents you just hated or something.'"'
Wendy, after seeing 'Dipper's birthmark, Gravity Falls