at first I was scared and yelled HOLY SHIT! because at first I thought it was just a ender holding a white block over it's head..then I realized the block was the head.
then I thought he was funny and also annoying because (don't worry we were playing on creative mode) he just stood on the roof of the castle me and my older sister made. he stood there and held a block.
then later he appeared in one of the rooms of the castle and we had a dance party around him and I accidently threw a snowball at him and he vanished.
also he is according to my sister (she is 20) he is now friends with steve. :/
I don't think so. I heard some facts and there is a 20% chance of getting an EnderMan with a SlenderMan skin. I even went into MineCraft files and the EnderMan skin I clicked had the SlenderMan texture. But it would be pretty darn nice for a Halloween texture pack~!