While it is not known to evolve into or from any other Pokémon, it has an alternate form, which it changes into by using the Prison Bottle. Its default form, Hoopa Confined, will then become Hoopa Unbound. Hoopa Unbound will revert into Hoopa Confined if three days have passed after using the Prison Bottle or if it is deposited in the PC.
Hoopa Confined was officially revealed in the February 2015 issue of CoroCoro magazine. Hoopa Unbound was officially revealed in the May 2015 issue of CoroCoro magazine
This section temporarily contains information copied directly from Bulbapedia, and needs to be rewritten so not to be classified as plagiarism.
Hoopa Confined is a light purple Pokémon with several pink markings. There is a v-shaped marking on its chest and bands around its wrists. Additionally, there are pink markings around its head and a growth on top resembling hair tied into a ponytail. There is a yellow, ring marking in the center of its forehead, and it has green eyes with yellow sclera. On either side of its head is a dark gray horn that curves slightly upward. Hoopa has three gold rings: one large one around its lower body and one hanging freely on each of its horns. Its arms are not attached to its body and float next to it. Each arm has a small golden spike on one end and a hand similar to a mitten on the other. There is a golden spike on each shoulder, which is similar to those on its arms. Hoopa's lower body consists only of a wispy structure similar to its ponytail.
Hoopa Unbound has a similar color scheme to Hoopa Confined, although the main color is now a light blue and its markings are slightly darker. This form is bipedal and has six arms. The ponytail on its head is larger and bushier, and its eyes are now yellow with white sclera. Its horns are darker and less curved with spiky, purple markings at the base. This form has a pointed, dark gray snout and a mouth full of pointed teeth. Several tufts of purple fur surround its body waist. Each of its arms is disconnected from the body and has a gold ring on one end and a three-fingered hand on the other. The uppermost pair of arms has a ring around each wrist as well. Many other rings are present on this form: there are two around each ankle, two around the base of its ponytail, two at the base of each horn, one near the center of each horn, one around its waist, and one encircles a black hole in the middle of its body. The circular mark on its forehead also surrounds a much smaller black hole. A purple stripe extends down each leg, widens at the knee, and makes a circle around the tip of the foot. Additionally, this form has a tail with a purple stripe along the top and arrow-shaped tip.
Hoopa has the power to transport things using teleportation, which warps space.