This goes with a Big MathsJam talk from 2015.
Dobble cards are points on a projective plane.
Each line contains all of the cards with a given symbol.
But a projective plane is its own dual: ifyou swap the lines and points, you get the same structure!
So there's no reason you shouldn't replace the symbols on a Dobble card with more Dobble cards.
DOBBLECEPTION!