“There’s a fine line between genius and insanity,” said Oscar Levant, the entertainment Everyman of the mid–20th century. “I have erased this line.” Coming from Levant, this clever turn of phrase holds a weightier truth. His encounters with “insanity,” as he put it, were well documented during the later stages of his career and they serve as the theme of Good Night, Oscar. With Sean Hayes starring as Levant, the talk-show icon’s sharp wit and ready humor are not lost on the audience. And yet the somber reality of his struggle against mental illness and drug addiction directs the play’s course. Good Night, Oscar ends its Broadway run this summer—don’t dally and risk missing it. For his performance, Hayes won the Tony Award for Best Leading Actor in a Play. —Jack Sullivan