What's a common nickname for people named Jared? Red.
Mr. Fish's comical ambivalence/hostility toward Jared takes on new meaning when you consider that Jared doesn't know how to use Pokeballs. He never actually captured Mr. Fish. Mr. Fish is still a wild Pokemon. On the other hand, it also shows the deep bond they share. When Jared is given a gift Pokemon and breaks the Pokeball, the Pokemon runs off and Jared merely assumes it's not well trained. Compare to Mr. Fish, who sticks with him despite his frequent behavior problems. "Dream Time with Mr Fish" reveals that he really does love Jared. However, this does explain why he needs don't eat Jared as a move, and why he's able to make his own decisions regarding which moves he forgets.
Volt mentions that he was born with Nomura syndrome but doesn't look like he was infected. Volt was designed by Nomura himself and people seem to forget that he's capable of designing non-bishounen characters; for bonus points, Volt goes on to mention Xaldin, Cid, and a few other non-bishie Nomura characters.
Although there is some Heartwarming in this as well, since Mr. Fish is able to choose which move to replace Hyper Beam with and actively avoids deleting "Don't Eat Jared", demonstrating that he genuinely cares about Jared and doesn't want to hurt him if at all possible.