Bioluminescence is the light that fish give off when they are in the deep layers of the ocean. The layer is called the abyss layer.

Sheldon and Amy go to the coffee shop where they first met to find a clue about the gift that Leonard and Penny left them. They rationalize their findings even though their rationalizations seem like a huge, unrealistic stretch

Sheldon uses positive reinforcement to change Penny by giving her chocolate when she “obeys” him.

The Octonauts sing about slimey sea creatures and their characteristics.

Sheldon buys a bunch of cats to cope with his break-up with Amy. He must pay $20 to get people to take his cats.