Chest Mimic
The Chest Mimic is an EXCLUSIVE pet that was sold in the Exclusive Shop. It was one of the first sold and is no longer available. It looks like the chests in the Town area.
The latest Pet Simulator X value list for Chest Mimic can be found below:

Regular
💎 48,000,000,000 (48b)

Golden
💎 Not Available

Rainbow
💎 Not Available

Dark Matter
💎 Not Available