Screamer

Screamers are tall, grey enemies that slowly move around the room. If Isaac gets too close to one, it will scream, paralyzing Isaac.

After it screams, its speed will drastically increase, and it will try to chase Isaac down. It will also gain a black aura around itself that will slow Isaac down if he's within it.

Trivia

 * Screamers appear to be based on the ReDead enemies from The Legend of Zelda, who are also tall, skinny enemies with a paralyzing scream.