Pickups (e.g. hearts, coins, keys, bombs, etc.) are attracted to Isaac.
The attraction enables the item to pass/fly over pits or rocks, but not through Key Blocks.
Hearts are only attracted if Isaac could pick them up with his existing Red Heart containers.
Batteries act similarly to hearts in that they will only be attracted to Isaac if his active item isn't fully charged.
Chests near Isaac open automatically. Spiked chests are opened without damaging Isaac. Locked chests and stone chests are not opened and still require a key/bomb. Can also open chests in Challenge Rooms without starting the waves.
A few enemies (like the Horf) are drawn toward Isaac as well.