A number of enemies in the Pikmin series can revive after death if their body is left alone. It is known that Spotty Bulbears and Gatling Groinks have this ability. When you kill an enemy that can revive, its HP will slowly regenerate until it simply gets up and continues attacking. To prevent this from happening, defeat the enemy while it is petrified so that its body disappears, make it fall down a hole (applicable in certain caves), return the body to the Research Pod or an Onion, or quickly progress to the next sublevel if underground.