Albino Snake With Two Heads

Bicephalic or tricephalic animals are the only type of multi-headed creatures seen in the real world and form by the same process as conjoined twins: they all result from the failed separation of monozygotic twins. One extreme example of this is the condition of craniopagus parasiticus, whereby a fully developed body has a parasitic twin head joined at the skull.
Occurrences
Two-headed people and animals, though rare, have long been known to exist and documented. The "Scottish brothers" were conjoined twins, allegedly dicephalic, born 1460 (dates vary). (Human conjoined twins, not all of the dicephalic type, have been documented since 945.)