With his curious, playful personality and expressive eyes, it is tempting, aquarium officials say, to think of Mit as a big, slippery toddler. (The giant bottle of formula does not help.) He still needs — and receives — a lot of human contact. “He likes us to be physical, grab his flippers and roll him over,” Ms. Hiatt said. “And he still really loves to snuggle in close.”

With his curious, playful personality and expressive eyes, it is tempting, aquarium officials say, to think of Mit as a big, slippery toddler. (The giant bottle of formula does not help.) He still needs — and receives — a lot of human contact. “He likes us to be physical, grab his flippers and roll him over,” Ms. Hiatt said. “And he still really loves to snuggle in close.”