Squash Blossom?

My neighbor, who I veggie garden with, and I can't figure out #1...what type of squash or whatever these plants are and #2...where the heck they came from! The leaves are huge, 12-14 inches across, the blossoms are really big too! The bees have been very busy pollinating those blossoms and now there are 'fruits/veggies/squash' or what, we don't know, developing. We think that maybe the seeds were originally in compost or maybe volunteers dropped by birds or squirrels. Who knows. Stay Tuned :)