Here's the thing about Anna and the King of Siam: They're two adults who behave like adults. Which is to say that they can be petty and small and stubborn — but at least their starting point is maturity. We don't see a lot of mature people in the theater these days. Like the movies, plays and musicals are skewing to younger audiences. Although the Muny's King and I was the twelfth Forest Park staging of this venerable Rodgers and Hammerstein musical since 1955 (St. Louisans are so spoiled), the beautiful Laura Michelle Kelly (London's original Mary Poppins) and the kinetic Kevin Gray (one of the very few actors to play the King on Broadway) made the familiar evening feel fresh by imbuing the stage with unpredictability, including sexual tension. Perhaps the Muny will reunite this appealing pair. May we suggest Oliver! — with Kelly as the doomed Nancy and Gray as Fagin?