Guts are a spherical enemy composed of a variety of internal organs appearing in both The Binding of Isaac and the Rebirth remake. They can be first encountered rarely in Chapter 2 but more commonly in Chapter 3 and 4.
Guts do not directly attack Isaac. Instead, they attach themselves to any environmental object, such as Spikes, Rocks, or even walls, and start rolling around them. They are commonly found in groups of two to six, and can damage Isaac easily if the player is not careful.