Hoppers erratically jump around the room, only jumping towards Isaac if he gets close to them. They can transform into a F. Hopper by touching a Fireplace.
After touching a Fireplace, Hoppers will become F. Hoppers. (Flaming Hoppers)
F. Hoppers behave similarly to normal Hoppers in that they will randomly hop around the room, following Isaac only when within a certain range. Unlike normal Hoppers, F. Hoppers will follow Isaac within a much larger and more aggressive range and also gain doubled HP, a doubled jumping distance, and a faster movement speed. Putting out all Fireplaces in an area with Hoppers is a recommended strategy to stop them from turning into F. Hoppers.
Leapers strongly resemble Hoppers in advanced state of decay and bleeding at the neck, yet possess at least doubled health. They deal the same contact damage and typically hop around blindly, but have a better sense of where Isaac is than Hoppers. What makes Leapers different from Hoppers is their ability to leap high into the air and land near Isaac's position, firing four blood projectiles in a plus pattern when they hit the ground.
Unlike Hoppers, they will not change forms when they touch a Fireplace and will take normal damage.