When does the next swan leave?

(Leo Slezak - world-famous tenor opera singer and also an actor/comedian in German films)

During a performance of Wagner’s “Lohengrin”, a technician sent the swan out too early before the tenor could hop aboard and the swan appeared onstage alone, drawing an empty skiff. During the ensuing flap, tenor Slezak’s voice was clearly heard from the wings, in the manner of an annoyed traveler addressing the stationmaster: “When does the next swan leave?”