If you were looking for the article about the Halloween 2019 pet with a similar name, then see Mutant Fox.
The Fox Mutant is a Legendary pet in Bubble Gum Simulator. It can be obtained by opening a Mythical Egg. The chance of hatching it is 0.05% (1 in 2,000) or 0.1% (1 in 1,000). with the Lucky Chancesgamepass.