"Stage-door Johnny" was a popular term in the New York City theatre of the 1880s-1890s, but it is largely historical today.
(Oxford English Dictionary)
stage-door Johnny slang (chiefly U.S.), a (young) gentleman who frequents stage-doors for the company of actresses;
1912 Out West Feb. 139/1 No theater can hope to do business without *stage door Johnnies.
7 January 1890, Chicago Daily Tribune, pg. 7:
New York World: A bomb has fallen among the dudes and the dugongs, also among the "chappies" and the "Charlies," likewise in the midst of the "cash" Clarences and the stage-door "Johnnies."
27 October 1894, National Police Gazette, pg. 6:
But the season is young, and so are the "Johnnies," and, as the proverb has it, "All things come to him who knows how to wait at the stage door."
29 January 1922, New York Times, pg. 32:
FIGURE OF THE PAST
High Cost of Entertaining Has
Abolished the Curb Line
of Former Days.
LIMOUSINES NOW IN WAITING
Higher Salaries for Chorus Girls
and Prohibition Play Part
in His Extinction