Soul
Pikmin Spirits appear every time a Pikmin is killed by a hazard or enemy. Although they are not visible when a Pikmin dies by falling into an abyss, it can be assumed that they do appear, but are out of sight.
They roughly resemble Pikmin's shape; however, they lack feet and leaf, bud or flower, and any identifying characteristics such as the Red Pikmin's nose. Their appearance is slightly transparent and they vary between the games.
In Pikmin 1, every Pikmin has blue spirit, irrelevant of the colour of the Pikmin itself, while spirits in Pikmin 2 are representative of the dead Pikmin's color. They also differ in size, most notable between those of Purple and White Pikmin.
Enemies
Enemies spirits have a pink-purple colour and look like a bubble with a more transparent "tail" trailing behind. Two holes resembling eyes are visible near the shape's centre. Bulbmin produce a smaller version of this type of spirit when they die. There is also a minor glitch involved with enemy spirits: if you kill an enemy and rotate the camera so that the beast is no longer on-screen, the enemy spirit will not ascend until it is once again seen.