This caterpillar is parasitized! Hornworms are commonly the hosts of the Braconid wasp Cotesia congregata. The wasp has a symbiotic relationship with a polydnavirus that works with wasp larval hormones and venom to stop the host from pupating, instead growing to a monstrous size. https://twitter.com/stringmousey/status/1250089538749333506

For more information:
https://onlinelibrary.wiley.com/doi/abs/10.1002/arch.940260209
and
https://en.wikipedia.org/wiki/Cotesia_congregata

This is Manduca sexta, the tobacco hornworm. they are sold as food in pet stores, are agricultural pests of plants in the Solenaceae family, and are commonly raised as moths as an educational or recreational activity.
http://entnemdept.ufl.edu/creatures/field/tobacco_hornworm.htm#desc

It's commonly confused with the similar tomato hornworm, Manduca quinquemaculata
Tobacco hornworms: red horns, diagonal white lines with black borders, no horizontal markings
Tomato hornworms: dark horns, diagonal and horizontal white lines with no borders
https://en.wikipedia.org/wiki/Manduca_sexta

https://twitter.com/darlingbeetle/status/1250486928136380417?s=19