This insect is about the size of a penny, 18 legs with fur / hairs on each leg, a light green colour, and was found in Ontario, Canada.
Your photo is of the Crowned Slug caterpillar. The later instars have red dots along the center of the back. What looks like all the legs are spines. The adult is a moth.
These are found in the woods. Larva feed on leaves of many trees especially oak, but also cherry, hickory, maple, basswood, beech and elm. They overwinter as larva.
This is one of the stinging caterpillars – the bristles are filled with poison to defend themselves from predators.