Yes, clearly the squash you got the seeds from was raised near some other squash.

While I suppose it's possible the parent plant was grown near other types of squash, I understand delicata in all cases is not a hybridized plant. Also, if it's possible for a cross pollinated flower to produce viable seed different than the mother plant (natural hybrid), it's news to me. I'll check into that idea. I also plan on saving seed from this plant and try it again next year with some separation from the others to see what happens. In the first photo, it's 6" x 3". The second is a couple feet away and measures 8" x 6.5". Notably it's not the size so much as it appears swollen and smooth, like a melon. An no, I have no melons this year.

And my original seed was from grocery store produce.

It doesn't matter if Delicata is a hybrid. If the squash plant you got the seeds from was near another squash plant, the seeds from it may well be a new hybrid. But yes, if so, and if you save seeds from this plant and plant them next year well isolated, there's really no way to predict what you're going to come up with.

What you have growing nearby this year doesn't bear on what the fruit produced nearby look like this year. Melons are cucumis, and Delicata is cucurbita, so I think such crossing won't happen, anyway. But there are plenty of cucurbita squashes that are swollen and smooth.

It's always been my understanding that squashes can cross pretty easily.

I don't think the plants need to be all that close either - bees and other pollinators can range pretty far.

That doesn't mean you can't use the resulting fruits, of course. They may be great, or they may be meh, but they're still nutritious.

This is why it's recommended to buy seed from seed companies.

Concur: Bees have a pretty wide range. One old time rule was a quarter to a half mile separation. Bees travel greater distances but not usually between flowers before returning to the hive..

Wanted to update this discussion. I harvested one of the larger squash and it weighed in at 4.3 pounds! No word yet on internal appearance or taste. I'll be saving some of the seed for next spring to see if one of the hybridized parents reveals itself. ~doug

Okay last update, I promise. The website would not let me edit after 24 hours.

The experience did not turn out well. After curing on the vine we tried one out. The pulp was very pale yellow to nearly white. It had the stringy nature of a spaghetti squash very dry, tough, and nearly tasteless. We did not keep it.

Lessoned learned? While we often hope a hybrid combines the best traits of the two parent plants, it just as easily turn out poorly.

Delicata, zucchini and other summer squash, spaghetti squash, some orange pumpkins, and unfortunately, toxic ornamental gourds are all in the same species Cucurbita pepo and can cross easily. It seems that the delicata you bought last year grew near a spaghetti squash, and the seed you planted was pollinated b y that. If any of the others are bitter, they are likely crossed with toxic ornamental gourds and you should not eat them even if you don't mind the bitterness. Winter squashes in the C. maxima or C. moschata species don't have this problem because all of the squash in their species are generally edible and similar enough that crosses are also fine to eat.