A celebrity is one who is known to many persons he is glad he doesn’t know.

H. L. Mencken (1880-1956) American writer and journalist [Henry Lewis Mencken]

A Little Book in C Major, ch. 5, § 5 (1916)
    (Source)

Variants:

CELEBRITY. One who is known to many persons he is glad he doesn't know.
[A Book of Burlesques, "The Jazz Webster" (1924)]

A celebrity is one who is known to many persons he is glad he doesn’t know.
[Chrestomathy, ch. 30 "Sententiae" (1949)]