When Slowbro [[Mega Evolution|Mega Evolves]], it becomes engulfed by the Shellder so that only its head, arms, and white-tipped tail are visible. Its head pokes out of the mouth of the Shellder and is surrounded by Shellder's now larger teeth. The spiral Shellder now has an opening at its tip, allowing the tail of Slowbro to stick out. Mega Slowbro balances on its tail due to its legs being engulfed. It 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 spots 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 an armor so hard that nothing can scratch it. Slowpoke is virtually unchanged, but it gains some power and motivation from Shellder's digestive fluids.
In [[Galar]], Galarian Slowbro's appearance is due to Shellder biting its arm instead of tail, causing a chemical reaction with the consumed Galarica
seeds within its body. The Shellder attached to its arm resembles the Shellder tail from its Kantoian counterpart but smaller with a purple tip shaped like a stinger . It has a slight color difference with purple spots on its forehead and belly. Its paws are also purple. It mouth is also colored dark light purple.
Galarian Slowbro are considered highly dangerous due to it attacking indiscriminately attacking its surroundings. The reason for that is due to Shellder unconsciously biting down hard on its arm at sometimes. While normally zoned out, its expression will quickly change when facing a strong opponent due to the stimulus jolt from its nervous system. Galarian Slowbro can move with speed that puts the quickest of known reflexes to shame in order to fire a liquid poison shot from Shellder’s tip<ref>https://swordshield.pokemon.com/en-us/expansionpass/pokemon/galarian-slowbro/</ref>.