An explination?

Edmund Kean made his debut at the age of six-and-a-half, where he played a goblin in Drury Lane's production of Macbeth starring, of course, Mrs. Siddons as Lady Macbeth. Her brother, John Phillip Kemble, took the titular role.

During the witches' incantation scene at the beginning of Act IV, he and a number of other goblins were suppsoed to run out onstage and cluster around the mouth of the cave. Kean arrived last and had difficulty stopping; he ran into another goblin and everyone tumbled down in a domino effect.

The scene was, predictably, ruined.