I'm a lazy composter. I just throw my garden/fruit/veggie scraps in a pile outside and let it sit. A year later, it turns into compost, but many seeds survive the process. As a result, I get kale and tomatoes and squash growing out of my compost pile, and mystery squash growing in my garden. I thought these two were going to be zucchini when they started growing because they were dark green. But they were growing short and stubby instead of long and slender. As fall approached, they started turning orange, so I thought maybe they were pumpkins. But they didn't get round and dark orange like pumpkins.
Last week I plucked them off their vines and cut them open. They looked like squash inside. Imagine that! They both had the little round cells that I'm used to seeing in spaghetti squash, so I cooked them accordingly. They didn't shred quite as easily as spaghetti squash after cooking, though. I'm guessing they were some mutant, cross-pollinated version. They tasted fine, and we're all still alive, so I call it a win.
I used the small one for Squash with Curried Apples and Turkey (pictured below), and the large one for gnocchi. Hooray for free volunteer vegetables!