Crayfish

Crayfish AKA Cray is a young, intelligent crayfish who has a bad leg related to their lab creation (following the eugenics incident). She is first teased in season 1 and fully revealed on the first episode of season 2 to the rest of the (main) fish.

Undercover Arc
The undercover arc takes place shortly after Crayfish's arrival in season two. Crayfish introduces herself under the alias of Paulina, a medical student looking for participants in a new drug trial. She hands off a flyer to Oarfish, which provides details on the experiment and promises a large sum of money to participants.

Most of the fish agree to go, motivated for their own individual reasons. The following week, the fish arrive at a laboratory (which is stated by - to be near the University of Southern Atlantic). Crayfish greets them all at the door and proceeds to give them a

Present (Before)
Crayfish's sins have weighed heavy on her heart since her betrayal in season two and she is desparate to right her wrongs and leave her past with the hillbillys behind her.

While doing research at the University of Southern Atlantic, Cray overhears some fish

With a small search party, Cray decides to seek out the old hillbilly laboratory which existed during the great war. It is shown in both flashback and with Crayfish's narration that this laboratory was where hillbillys actively experimented on fish (mainly in the form of eugenics), created some of the most deadliest weapons known to man, and most importantly, ran operation IDTS - V1.14, which was the only successful time travel experiment. She states that though she was created in a different lab, her high intelligence made the hillbillys move her to this lab to conduct experiments with the other hillbilly scientists. When asked how many other fish were created from lab eugenics, Cray states she doesn't know, however most of them were killed for their imperfections. This was one of the biggest motivators to keep her working with the hillbillys, stating that as long as she kept working to improve hillbilly technology, they would set the fish free instead of killing them. She does not know if they ever kept their promise, though she suspects they did not.

Past

Future

Past

Future (FAN SPECULATED)

Memories Arc