My caterpillar hasn't been moving. What's wrong? Is it dead? Should I move it to another leaf? Put something else in there? HELP! I'm frantic! I'm in a panic!Okay, it is time to RELAX! That's right. Relax. Breathe. Chances are that your caterpillar is ready to molt. Shed its skin. Change instars. Grow. Become a bigger caterpillar. And, all your worrying is for nothing! In fact, if you 'bug' the little guy, he/she is NOT going to be pleased at all and you might do more damage than good.
Butterfly larva go through several instars. Each time, they will molt or shed their skin because they outgrow the skin that they are in. When it is time to do this, they often will go to find a nice, quiet place and stop moving, sometimes for around 24-hours or so. With Monarchs, a lot of times, for those of us who raise them indoors, the perfect spot might be on the top (lid) of the rearing container. For others, like this Gulf Fritillary (Agraulis vanillae), it might be on a leaf.
This little guy just molted and has moved away from his exuvia and is letting his 'new' outer skin dry. Soon, he will go back to eat the exuvia. 
It takes time for the skin to come off then time for the caterpillar to turn around and go back to EAT the skin. Here's an Anise Swallowtail (Papilio zelicaon) who is just getting started on the munching. If you are fortunate enough to watch this, it is quite fascinating! Click on the picture for a close-up view.Remember, if the caterpillar is still, it hasn't moved in some time, then leave it alone!~ Do not touch it. Do not move it. Do not force it onto a leaf. Do not do anything but leave it in peace.
SO, if your little caterpillar doesn't move for awhile, what are you going to do? Leave alone, right? Good! Soon, your little one will be a BIGGER one!