No, Creepy Mutants only serve as enemies in The Forest. At no point in time are you able to interact with any of them as an NPC, much less befriend any of them. You do engage in battle with many of them, and they can destroy your base if you are not careful. In the sequel, Sons of the Forest, it is hinted that you will be able to meet some interesting new Mutants that have not fully turned yet. It is slated to be released in 2022.