The nurse telling the soldier "It's a boy Captain Walker, it's a boy" is reference to the opening lines of the The Who's seminal album "Tommy" (1969).
The title refers to a symbolic ceremony that someone has passed from one stage of life to another such as with the Hebrew Bar Mitzah for passing from childhood to manhood.
While he is in his hospital room, Michael Skelton reads the comic books Batman: The Dark Knight Returns #2 (July 1986) and Daredevil #241 (April 1987).