Just got 18 up and running and took a look at he coding for the change marker and found the following in the code. So far I have not figured out quite what is needed to trigger the Easter Egg.
! ===================================================================
! Draw Easter Egg if there is
! 8 polygon node
! with 8 perpendicular angle, 2 flat in one upper and 4 lower (club-feet)
! boundary is Random Radius
! ===================================================================
