There is a hidden island inhabited by Steve and some chickens in the mission called "Operation Charlie Takedown". Saving Steve aka "Blockhead" is one of the steps needed to unlock an in-game achievement called "No Stone Unturned", which requires finding all secrets.[2]
In Caustic Caverns, creepers can be found in a hidden cave, along with several breakable blocks, including dirt, stone, and coal ore. When killed, they can drop weapons themed after Minecraft. Steve's head is a wearable item in the game.