Rex Buifloatzel

Rex is a half-evolved Buizel/Floatzel. He's no longer able to fully evolve, so is stuck at this in between state instead. (He classifies himself as a Buizel. In official representations, he's a Floatzel)

He got pretty beat up in an attempt to save his partner as well as water hazards that wound up leaving him scarred and missing his left fin.
Washing up on shore after the worst of it, just barely clinging to life, Rex was discovered by a human, and the next thing he knew, he was recovering in the care of a scientist (with frequent check ups from the professor and the local nurses to study his recovery and to make sure he was still on track to be able to return to the wild one day)

Rex wound up with memory loss issues while he was with his previous partner. The solution to that was the green stone that he now wears around his neck at all times. He's not sure how or why it works, but by keeping it close, it's like his memories are stored within it. When he's lost in thought or trying to really remember something, he often holds on to this gem and rubs it without realizing that he's doing so. This stone is green and has a soft glow to it that only gets stronger when in active use.

It can be thought of as an external memory drive for his brain. Though it only retains memories that he's had since obtaining the stone, so there's still a lot of his life lost.