Was it at least a snake so we could have the live action version of the movie?

That would’ve been amusing.

I've seen a dog running around the crew room a few times. I just assumed it was where Notorious Billy dropped it off before doing a PAP turn.

So, uncommon opinion, but many states say they requre a health certificate to accompany any domestic animal that is transported into that state. You can check the list here at the USDA site:

https://www.aphis.usda.gov/pet-travel/state-to-state

The vet certificate isn't hard to get, but it is only good for 10 days. The chances are no one will ask you for one these days, but if you are carrying on an animal and paying the fee, there is a small, but real chance you could get asked to produce it. You'll need to show the animal is vaccinated, and looks healthy. If you choose to ship the cat as frieght, you probably will be asked for the certificate.

Cats do not like to travel. Period. It was bad enough before, when airlines limited the number of carry on animals (1 per cabin, for example), but with people not only carrying on animals but letting them roam free, you introduce a real hazard to the animal and yourself. It's best to medicate the cat if you can. If you go the vet certificate route, you can ask the vet ahead of time to order Pregabalin solution. It's sold as "Bonqat" in the States, and is a liquid, non sedative medication that will seriously chill the cat out. You need a prescription, but is inexpensive and, is a relatively easy to administer liquid (you give it 1.5 to 2 hours ahead of travel), and it will seriously mellow the cat out for the rest of the day. Do you and the cat a favor.