Okay, I consulted my "Caterpillars of Eastern North America" book. There are a LOT of caterpillars that eat apple. But knowing the host plant still eliminates a lot of other caterpillars. It looks most like the Ashen Pinion (Lithophane antennata) in my book, although it says there is a similar Broad Ashen Pinion (Lithophane laticinerea). Known commonly as Green Fruitworms, it says they rarely eat the actual developing fruits.
Here's a link to an ID book on Google Books. If you read the behavior part, he was making his mad face at you!
https://books.google.com/books...
