Yadoran

Slowbro is a bipedal, pink Pokémon with a tan, striped belly and a rounded, tan muzzle. It has large, vacant eyes, curled ears, and two small pointed teeth protruding from its upper jaw. It has three clawed fingers on its hands and two clawed toes on its feet. There is a Shellder attached to its tail. This Shellder has a gray, spiral shell with darker gray spots and small, triangular eyes near the base. There are several spikes across the surface of the Shellder, and it holds onto Slowbro with many sharp teeth. Shellder developed its spiral form in an effort to suck more sweetness out of Slowbro's tail. If its tail or the Shellder attached to it is broken off, Slowbro will revert to its unevolved form, Slowpoke.

Slowbro has lost the capability to feel pain due to the Shellder's poison. While typically lazy and unintelligent, Slowbro apparently becomes inspired when the Shellder bites down on its tail. While it is capable of unleashing powerful psychic attacks, Slowbro is typically rather peaceful and usually prefers not to fight. Because it can no longer fish using its tail, it instead swims to catch its prey and allows the Shellder to feed on its leftover scraps. Slowbro tends to live near ponds, lakes, and seashores. As mentioned in Pokémon Sleep, Slowbro usually sleeps at the same time as the Shellder biting its tail. On occasion, it sleeps even when Shellder is still awake.

Forms
Slowbro can Mega Evolve into Mega Slowbro, and has a regional form, Galarian Slowbro.

Mega Slowbro
A Mega Slowbro, it becomes engulfed by the Shellder so that only its head, arms, and white-tipped tail are visible. Its head pokes out of the Shellder's mouth and is surrounded by the Shellder's enlarged teeth. The Shellder has holes on its sides and an opening at its tip, allowing Mega Slowbro's arms and tail to stick out. Mega Slowbro balances on its tail due to its legs being engulfed.

Mega Slowbro can move by bouncing, using its tail as a spring. The spikes on the Shellder are now reduced to four on the bottom section of its body and the dark spare dots are only visible on its middle section. Mega Slowbro's energy has gathered into Shellder, which has increased its hardness. This allows it to act as armor so hard that nothing can scratch it. The Slowbro inside is virtually unchanged, but it gains some power and motivation from Shellder's digestive fluids. Mega Slowbro can create water tornadoes to attack foes.

Galarian Slowbro
In Galar, Slowbro's appearance differs due to Shellder biting its arm instead of its tail, causing a chemical reaction between the Shellder's poison and the consumed Galarica Twig spices within the Slowpoke's body. The Shellder attached to its arm resembles the Shellder tail of its Kantonian counterpart, but is smaller, with a purple tip shaped like a stinger, and lacking visible pupils. Galarian Slowbro itself has a slight color difference compared to its counterpart, being pinker, with purple accents on its head, arms, and tail.

Galarian Slowbro is considered highly dangerous for its tendency to indiscriminately attack its surroundings, the reason for which is due to its Shellder sometimes unconsciously biting down hard on its arm. Another reason is that Shellder feels bliss when biting hard enough to absorb Galarian Slowbro's poison. However, Shellder will occasionally faint from the seeping poison, and Galarian Slowbro occasionally lashes out due to the itching caused by said poison. While normally zoned out, when facing a strong opponent its body becomes stimulated, and it will sport a sharper expression. Galarian Slowbro attacks by grabbing at its Shellder's tongue, causing the Shellder to fire poisonous liquids from its tip. It attacks at speeds rivaling the quickest of known reflexes. They can also be found in the Coastal Biome of Blueberry Academy's Terarium, where Galar's regional life is simulated.

Evolution
Slowbro evolves from and is one of its final forms, the other being .
Galarian Slowbro evolves from Galarian Slowpoke. It is one of Galarian Slowpoke's final forms, the other being Galarian Slowking.

(Source: Bulbapedia)