know someone when

From the formulaic phrase by which speakers begin reminiscence of now-famous persons.

know someone when (third-person singular simple present knows someone when, present participle knowing someone when, simple past knew someone when, past participle known someone when)

1. (usually in the past tense) To have known a famous person before he or she was famous.
   • 1915, "Interesting People: Charles Bullard: A Famous Photographer of Cats", in "The American Magazine"

     His friends thought him crazy, as friends always think when a man has an original idea and acts on it. Now, when his friends speak of him they invariably add, "I knew him when—"

   • 1918, Western Electric News:

     Of course when your school chum comes in from the old home town you want to send him back a life-long member of the "I-knew-him-when Club." You picture him back home, just a wee bit superior, as befits a friend of the great, holding forth to the boy's at the Sunshine Athletic Club.

   • 1920, George Ade, I Knew Him When--: A Hoosier Fable Dealing with the Happy Days of Away Back Yonder:
   • 1971, W. A. Mambert, The Elements of Effective Communication: Idea, Power, Tactics, page 146:

     The classical example of this is the "I knew him when" syndrome. Consider your immediate family. They know you as you really are, if anyone does.

   • 2008, Lisa Tucker, The Cure for Modern Life, page 89:

     "Well, congratulations. On the speech, everything." She stood up straighter and forced a smile. "I can always say I knew him when."