This egg was only available in Egg Cave's Cash Shop Park for December 2013.
Bomnoms are an electric species. Bomnom eggs are not well-insulated, so they leak electricity. If you put a Bomnom egg on or by something particularly conductive, prepare for a little extra shock (it's not lethal, but can cause nerve damage)!
Based on genetic anomalies uncovered by the Science and Research Center, it is believed that Bomnoms predate the Second Drowning of Ark. There is nothing particularly aquatic about them, so how they survived in the oceans without any land remains a mystery.
Very little is known about Ark before the Second Drowning. Based on fossils extracted from the deepest rock in the island, it is believed that there were a limited number of species that lived on Ark, Bomnoms one of them. The most ancient Cave runes show that these original species fought over the island's power and energy. Humans, in these ancient runes, seemed to have regarded Bomnoms as "the Guardians." However, it is not known what they were protecting the island from.
Lastly, Bomnom's electric energy is strongest during the months of December and January, peaking at Christmastime.