To me it looks like a rugular jack o lantern pumpkin. Mine look like that and they are Connecticut field pumpkins. Did you throw out last years pumpkins in this spot?

I didn't grow any pumpkins last year. In prior years I've grown jarrahdale, cinderella and giant atlantic.

Pumpkins and butternut squash volunteer frequently in my garden.

I hope it's not just regular. I like it that it is turning out to look exotic, perhaps like the one in this link.

Here is a link that might be useful: One Too Many

Be careful about volunteer pumpkins. It can be hard to insure the seed quality if the pollen came from an unknown source and you could end up with a rather disgusting hybrid.

Disgusting in taste? What about the seeds? Fortunately for me, I only use the pumpkins for decorating and seeds. I'm becoming convinced it's some crazy hybrid. But it sure is pretty so far.

"To me it looks like a rugular jack o lantern pumpkin. Mine look like that and they are Connecticut field pumpkins."

I am a bit confused at that, since as I understand it, there actually is a species called Jack-o Lantern, and then there is another called Connecticut Field.

As long as you don't plan to eat the fruit, you may end up with a funky shaped pumpkin but the seeds should be fine to eat. And yes, I meant disgusting taste in terms with the flesh. Possibly very watery, stringy, or bland tasting.

It is just a regular pumpkin. If you don't know it will turn from green to orange as most pumpkins do. The varieties that you listed having grown before all can start off as yellow turning to orange, which may be why you think this one looks strange. It is not a one too many, I have grown them before and that is not what the immature fruit look like.

Obsolete, when halecards said jack-o-lantern they were referring to the type of pumpkins used to make jack-o-lanterns, not a variety. Which is what connecticut field is, many people refer to large orange pumpkins as jack-o-lantern type pumpkins. Also just to be clear they are not different species, they are both Cucurbita pepo, they are different varieties.

All my past pumpkins started out green and turned orange (or blue-green in the case of the jarrahdales). What seems unusual about this one is the stripes and veins.