PPMC is the name of Dan's starship in Through the Wormhole. Her acronym means: "Precambrian, Paleozoic, Mesozoic, Cenozoic Project".
A "claxton" is a male siren. Therefore, Tracey in the Metamorphosis/Claxton stories comes from a watery background.
A "Magic Animal" in the Metamorphosis/Claxton stories are animals that are born in the Magic World, rather than the Human World.