Wildlife Spotting

Definately the Vine Hawk moth (green form): http://lepidoptera.butterflyhouse.com.au/sphi/celerio.html

By imitation grape vine, do you mean a fake (plastic or silk) one? That would be pretty funny since it uses real grape vine as a host plant. I see that Hippotion & Sphinx are synonymous.

I'd say it's a sphinx moth larva. They always have a large horn at the tip of their abdomen and no hairs.

He looks like he overate.

I believe it's a type of swallowtail caterpillar