The overalls. The pigtails. The eyebrow-penciled spray of freckles on the cheeks.

Anyone with even a passing familiarity to children’s theater knows (and probably dreads) the telltale signs of grown-ups playing kids on stage. Lisps are not uncommon.

But several recent plays, including Clare Barron’s acclaimed “Dance Nation” and the current Roundabout Underground offering “Usual Girls,” by Ming Peiffer, have ditched the usual cloying tropes. Ms. Barron’s stage directions even say, “Cuteness is death.”

In an era when audiences and actors alike expect to see traditionally underrepresented demographics portrayed by actors from those communities, age has become a more fluid concept to explore. (This also allows for provocative content that would be questionable at best with actual children involved.) Not the mild suspension of disbelief wherein 23-year-olds play high school sophomores on TV — some things will never change — but a more drastic shift appears to be underway onstage.

The most visible current example of this can be found at the Shubert Theater, where three pivotal roles in “To Kill a Mockingbird” — Dill, Jem and the play’s narrator, Scout — are being played by performers double and triple the characters’ ages.