Chupacabra was a skin added in 2016 as part of the Cinco de Mayo update. It could be purchased for a limited time in the agario store for 4900 coins. It is the most expensive skin in the Cinco de Mayo update.
Note: Chupacabra was released again for a limited time under the 5 De Mayo offer in early May 2020. This time Chupacabra could be purchased for 6100 coins.