I genuinely cannot imagine that. It doesn’t make any sense. The only property that is a necessary condition for an egg to be a chicken egg is that it has the potential for a chicken to hatch from it. So what you are describing has an inconsistency and is therefore nonsense. Do you mean an alligator egg that looks like a chicken egg? Because if so, then it’s still an alligator egg.

Literally the only thing that matters is that an alligator hatches from it, so it’s an alligator egg.