This past weekend, the lights of the Ruth Nagel Jones Black Box Theater shone brightly on a giant pride flag painted on the stage. The occasion was Wellesley Upstage’s production of “Head Over Heels,” a jukebox musical featuring the music of the Go-Go’s directed by Taryn Castro. 

When you see a production of William Shakespeare’s “Twelfth Night,” you might expect to see bouquets of roses, character disguises and hear lots of “thines,” “thous” and “dosts.” You...