Cherrim is a small Pokémon with two different forms, both of which are dependent on the weather. During normal weather conditions, Cherrim is in its Overcast Form. Two purple petals enclose its deep pink body. A short purple stem and a green leafy sepal sprout from the top of the petals. Its eyes appear to be near its short legs in this form.
When there is strong sunlight, Cherrim is in its Sunshine Form. Pink petals similar to cherry blossoms surround its head and cover its chest. Several of the petals radiate outward from a yellow sphere on the back of its head. There is a small, triangular patch of green on its neck. Additionally, two berry-like orbs, resembling cherry-shaped hair ornaments, adorn its head. It has stubby limbs, with the arms being pink and the legs being yellow.
Cherrim waits quietly as a bud for a ray of sunlight. When it is hit with strong sunlight, it blooms and absorbs the rays with its entire body. It quickly changes from quiet to excitable and active. It will attempt to make up for everything it had to endure as a bud while the sunlight lasts. Once the light is gone, Cherrim folds back into a bud. Cherrim was briefly the only known Pokémon capable of learning Flower Shield in Pokémon Sword and Shield.
In Promoting Healthy Tangrowth!, a Cherrim assisted a Tangrowth and other Pokémon during several attempts to restore a damaged 1,000-year-old tree back to health.
While Cherrim's forms are called Overcast Form and Sunshine Form in English, the Japanese names of its forms use 「フォルム」 form, which is otherwise only used in the names of forms which are localized as Forme.
Cherrim is the only Pokémon that can change between its forms during battle without the need of a move or ability.
The presence of intense sunlight can be brought on with Sunny Day and Drought, but Cherrim does not need to use these itself or be present during the activation of sunlight to change form.
Origin
Cherrim's reaction to light is apparently based on photonastic flowers. Cherrim Sunshine Form seems to be based on cherry blossoms, flowers that are particularly symbolic of Japan, while Overcast Form could be loosely based on a fuschia flower.
Name origin
Cherrim is a combination of cherry and cherubim or blossom. It may also involve cherimoya (a fruit-bearing tree) or tirim (Irish for dry, as in dry weather).