Green, very small and extremely spiky….found on my car in Enid, Oklahoma.
Your caterpillar is one of the slug caterpillars in the family Limacodidae…it is in the genus Euclea. Unfortunately without knowing the species , we can not give a common name.
Your caterpillar is related to the spiny oak slug caterpillar, but the coloration makes me think it is not that species. There are 3 species that would be in OK…and they all look similar enough that it would be hard to know which one you had. Unless perhaps you had the adult, but even 2 of the species of adults are difficult to tell apart without DNA coding!
This family of caterpillars are known to sting, so do not handle it!
These caterpillars turn into moths, some rather pretty brown with large spots of green.
This insect is found in eastern North America in deciduous forests. The caterpillars feed on apple, basswood, cherry, chestnut, maple, oak, redbud, sycamore, willow and many woody plants and shrubs.