It's a tomato hornworm. The white things are the eggs of a parasitic wasp.

It's best to just leave it be. The eggs will hatch and kill the hornworm, and the young wasps will go out into the world to seek and destroy more hornworms.

You don't really want hornworms eating your tomato plants. If you leave this one alone, the wasps that hatch from these eggs will help control your hornworm population.

-- BC --

Actually, that's a tobacco hornworm. The wasp cocoons are that of one of the braconids, a subfamily of solitary, parasitic wasps. Unfortunately, most braconids not only have a taste for sphinx caterpillars [including the 2 garden pest species], but relish all saturniids and the larger butterfly larvae as well.

It's too late for that cat. The wasps have fed and now pupated, themselves. The sphinx cat will die in the pre-pupa stage because the wasp grubs consumed all the caterpillar's fats. It won't have the energy needed to complete metamorphosis. Kill the whole thing, including parasites and maybe some other non-pest sphinxes and saturniids about will be around next year for you to enjoy. You can always give unwanted, but healthy hornworms to a local school or a nature center or even just kids who like to rear insects. It's a myth they have to eat your garden plants. The nightshade-eating Manducas are very fond of any solanaceous weeds you may have around.