NatureBunny is the name of the pairing between E. Aster Bunnymund from Rise of the Guardians and Mother Nature from Guardians of Childhood. Although not being a popular pairing in the fandom some fans still ship it.
Bunnymund apparently met Mother Nature once, and he is the one who seems to know about her personality the best, beside Sandy. He knows she isn't always kind and is very unpredictable.
The two are very ancient creatures who have a role in Earth's creation (Bunnymund shaped the Earth who had the form of an egg, and created life and spring while Mother Nature controlled the weather, such as wind, rain snow as well as earth). As Bunnymund knew Pitch's backstory that is also probable he knew Emily Jane's existence.
Their relationship would be difficult to handle because Emily Jane is Pitch's daughter who eliminated Bunny's kind. However, they could eventually warm up due to their connections to Earth and their roles in seasons.
Note: only post examples from within the RotBTD fandom.