| Gayspeak for being gay. Back in the day (approx. 1950s to 1970s) Are you a friend of Dorothy? was a code phrase that closeted homosexuals could safely use to identify each other while in the company of heterosexuals.
The most obvious explanation for Dorothy's identity would be Judy Garland's character in The Wizard of Oz. Garland was during her lifetime, and still is, an icon of the gay community, The Wizard of Oz being a particular favorite. Plus, as everyone knows, the Cowardly Lion is totally gay.
Dorothy Parker, a gay icon of a lesser stature, is another possibility. | 
