Toni worries that Max may become an "invert". This was an early 20th century term for gay people. Psychologists at the time believed that gay people had an "inverted" gender identity and believed that they were the opposite sex. So lesbians, in this theory, were attracted to women because they believed themselves to be men and men were supposed to be attracted to women. Max, with her monomaniacal obsession with the traditionally male pursuit of baseball, her new embrace of factory work, and her seeming rejection of the female world of the beauty salon, would have seemed especially susceptible to being an "invert".
The young boy sitting on the steps is reading Lightning Comics Vol 1 issue 4 (December 1940). His friend, leaning on the handrail, is reading Lightning Comics Vol 2 issue 3 (December 1941).
The episode title is a double entendre, referring both to a player who can bat both left and right handed, as well as someone who is bisexual.