It has been going through some changes.
One morning it looked like this. No worries though.
There's nothing wrong with it. The green caterpillar has entered the phase of the life cycle called the prepupa. It was ready to change into a pupa.
Sure enough, the next day it had pupated. Can't wait to see what the moth looks like.
Too bad the pupa isn't see-through like the caterpillar was, so we could see the changes happening inside.
Aside: Every year we expect to hear cicadas around Father's Day. Sure enough, Father's Day was Sunday and we heard our first cicada on Monday. Talk about sticking to a calendar!