This is neat little mod made by Exalm. Basically, like in early versions of Minecraft, you can press the G key in creative and it will spawn a human which will just run around aimlessly. The human has the exact skin of steve. The mod is basically just to get that really early feature that was taken out back in the game. People could get quite creative with this, like for making adventure maps or cinematic. Good job Exalm!