Here is our kind of Easter Egg! The "Shock Egg"!
A Vapour Cone, Shock Collar, Shock Egg or Cumulobadass (A term coined by the atmospheric researchers at Sierra Hotel Aeronautics)
The Shock Egg is nothing more than a visible cloud of condensed water typically observed as an aircraft, or object, approaches transonic velocity. Atmospheric dihydrogen Monoxide(Organic Chemtrails) then condenses, and thus becomes visible, as air pressure varies suddenly across shock waves associated with supersonic flow speed.
Atmospheric condensation around aircraft is also associated with low-pressure regions in subsonic flight, and can typically be observed in damp conditions; but this does not result in conical condensation clouds.
Shock eggs, or condensation cones appear in what is described as a Prandtl-Glauert singularity.
In addition to making the shock waves themselves visible, water condensation can also occur in the trough between two crests of the shock waves produced by the passing of the object. However, this effect does not necessarily coincide with the acceleration of an aircraft through the speed of sound or Mach 1.0.
Pictured Below: Easter Egg - A transonic US Navy COD pushing though the sound barrier on her appointed mail run...