It can be found at night rarely by default .cfg
Healed by explosives but not by each other's explosive moves; however, one move is summoning miniature Creepers, whose explosions do heal it.
5 different attacks and animations for each attack.
Melee Attack: the Mutant Creeper attacks with it's head and large appendages.
Jump Attack: the Mutant Creeper launches itself into the air and explodes on impact with a large blast radius.
Minion Attack: the Mutant Creeper spawns miniature hostile Creeper Minions; their explosions heal itself.
Charge Attack: the Mutant Creeper begins flashing and shining, if untouched it will heal itself for 30 hearts, it is vulnerable at this time if no Minions are around, however.
Lightning Attack: the Mutant Creeper summons a Lightning Bolt to hit itself, this charges it, making all of it's attacks stronger and blasts bigger; a charged Mutant Creeper also has charged Creeper Minions.
The Mutant Creeper will begin charging up, it flashes while sucking in any entity around it, until exploding ("/gamerule mobGriefing false" does not fully protect against the blast) and leaving behind an egg: the egg can either hatch into a Baby Creeper Minion, a pet most notoriously as PopularMMOs' "Bomby", or can be killed and drop 10 Gunpowder, and the Creeper Shard.