The Jellyfish

The jellyfish represents new beginnings and the possible. Melvin reverses his age due to the compound he's able to generate from the jellyfish. This leads to him ultimately spurring new beginnings for Ellie and Melissa and opening his mind to the point that he takes a bus to travel not knowing where he is going.

Eating the jellyfish at the restaurant with Raj and Melvin enforces the friendship between Ellie and Raj once she starts playing the crispy corn dog game with him (replacing the corn dog with the jellyfish).

Finally, the delivery of the jellyfish on the last page of the novel does not mark the novel's end. It is a beginning.

The Goldfish

Ellie receives a goldfish from her teacher at the beginning of the novel to teach her about the cycle of life. In the end she truly learns about the cycle...