Threshold

From a physical standpoint, a black hole is a marvelously simple object, far simpler then the earth or a human being... When a black hole first forms, its horizon may have a grotesque shape and may be wildly vibrating. Within a fraction of a second, however, the horizon should settle down into a unique smooth shape. If the hole is not rotating, its shape will be absolutely spherical. Rotation, however, will flatten it at the poles just as rotation slightly flattens the earth.

Kip S. Thorne 'The Search for Black Holes'