Omnom Snek is one of the three skins released in the multi-part Cutest Christmas offer. It could be purchased as part of an item deal in late December 2019.
Omnom Snek could be purchased for $14.99 in a limited time deal which included 35000 coins, 1500 DNA, a 2x Mass Boost (24 Hour), a 2x XP Boost (24 Hour) and the Omnom Lion skin. It was not available for individual purchase and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.