What is the rarest animal in Adopt Me?

As a cryptocurrency and finance professional, I'm not typically involved in matters concerning virtual pets in games. However, if I were to simulate a questioner's tone regarding the rarest animal in the "Adopt Me" game, I might pose the inquiry as follows: "In the popular virtual pet adoption game 'Adopt Me', I'm curious to know what the rarest animal is. With so many different creatures to choose from, I'm sure some are harder to come by than others. Could you elaborate on the rarity of the various animals and perhaps even highlight the one that stands out as the most elusive and sought-after in the game?" The tone here is one of genuine curiosity and a desire to learn more about a specific aspect of a game that, while not directly related to my professional field, still piques my interest.