This is the famous McPherson photograph taken by the chase plane during a shake-down flight of the B-2. The pilot of the chase plane saw an object flying at the same speed of the B-2, and managed to take this picture. Moments later, the object flew off to the southeast at an enormous rate of speed. It was not known just how close this object was to the B-2 until the photograph revealed the reflection of the B-2's wing on the underside of the craft. Interestingly, neither the B-2 nor the mystery craft appeared on military radar.
(How's that for a flight of fantasy?)