I'm just learning and could be missing something but after printing, the egg fit but the rabbit would not stand without tipping to the side. The Kinder eggs in my area have a lip attaching the 2pieces together and it's possible that lip was stopping it from fully being centered. I wasn't able to figure out a solution but didn't invest much time.
In my opinion, it has nothing to do with the egg, rather the printing, if your first layer is not good or there is a wider 'elephant leg', then it can happen that it tilts because the bottom is not flat.