Unwanted cars go to the scrapheap. Unwanted characters go to the Scrappy Heap. Scrappy's Heaps is a scrapyard that exists beyond the fourth wall as a refuge for hated characters.
An advanced aircraft prototype is stolen from Canterlot Aeronautical Laboratories. Searching for it are the Mane 6, Maverick, Goose, and a vanload of meddling kids and their dog.