To some, it might seem strange that the Easter Bunny, which is a mammal, would lay eggs, which is not a mammal trait. However, it might be a case of combining traditions, as eggs are also significant to modern Easter celebrations.

History notes that decorating eggs dates back to the 13th century when eggs were previously a forbidden food during Lent. To celebrate the end of Lent, people would paint and decorate the eggs and eat them on Easter in celebration.

Source: https://www.distractify.com/p/where-did-the-easter-bunny-come-from