Being like everybody is like being nobody.

Rod Serling (1924-1975) American screenwriter, playwright, television producer, narrator
(Attributed)
    (Source)

Frequently attributed, but never cited. In the Twilight Zone episode, "Number 12 Looks Just Like You" (ep 05x17), the protagonist comments, "But is that good, being like everybody? I mean, isn't that the same as being nobody?" That episode is credited to Charles Beaumont and John Tomerlin.