Dwarf rabbits

Dwarf rabbits are much smaller than normal rabbits, but are capable of interbreeding with them, so are not recognized as a separate species. Purebred dwarf rabbits weigh 0.7-1.4 kg. Their heads and eyes are disproportionately large with respect to their body, and their ears are small and carried high on the head. The exception to this is the dwarf lop — a cross between the French lop and the dwarf — which is both heavier (3.0-4.0 lb) than a standard dwarf and has long, dangling ears. they have fur to keep warm.
rabbits and other lagomorphs contain a lot of microfauna (bacteria) in their guts which helps them digest plant matter. This is a form of endosymbiosis in which the bacteria live inside the host.
Breeding two rabbits that both carry the dwarf gene may result in a homozygous dwarf offspring, that is commonly termed a "peanut". Peanuts (about the size of a peanut) are very small and deformed baby rabbits that will be born with a very large head, almost no ears and their back legs often cross. Peanuts usually live for a few days but sometimes will last a couple of weeks. The birth of a peanut proves that the dwarf gene was present in both parents.