>>716156164
They seem to just be literal easter eggs. But at the same time, they're tied directly to Kris's entire existence.
Gaster considers them as a direct contradiction to absolutely everything that he's trying to accomplish and if you get one egg he considers that chapter, "not completed". And if you beat the whole game while getting every egg, Gaster asks "What are you?" Implying that this is the influence of some third entity that isn't you or Gaster on the story.