Green pumpkin hybrid thing - identification

[zerocylinders]

Anyone want to tell me what kind of squash/pumpkin/melon I might have here?

I thought this was a watermelon .. .lobed leaves, and it started out with a very green, watermelon looking exterior, complete with watermelon type streaks on the thin skin. I had marked the plant as watermelon so I at least thought I had planted a melon and it sure looks like a watermelon plant but ..

A few days ago after very heavy rains and extreme heat, the stem started turning orange, the leaves started to wilt, and the skin started to get orange streaks. Pumpki-Melon!

I picked it since the plant looked bad (my zuchini plant also looks bad not sure if the rain and heat is just killing them or else ??).

Expecting a juicy watermelon, my wife cut it open and surprise .. .its a pumpkin. Sort of. Slight pumpkin smell, seeds definitely look pumpkin-ish. Hollowed out inside like winter squash. But green skin, and white-ish flesh?

The "watermelon" should have been either heirloom peacock or and crimson sweet. In the adjacent bed I have a Champion Pumpkin and a Zucchini (Black Beauty). Could the vines somehow have merged? Or is this just a very strange looking (and early) pumpkin?

Indidentally, the Champion pumpkin has a very nice orange pumpkin on the vine, looks NOTHING like this.

The bed has not been used previously, so I would rule out an old seed or vine. One clue might be that the "watermelon" seemed to be dead when I first transplanted it (from hydroponics; I started very early in March to get a strong plant by end of frost here in Chicago, but it did not appear to survive the transplant at first). It came back to life in late May and produced the "melon" only a month or so ago. The "melon" grew pretty quickly in a standard oblong watermelon shape, skin appearance, etc.

But obviously, not a watermelon when I opened it up!

I did save the seeds so next year will see what it produces, but any ideas what may have happened here?

Links are to dropbox ... hopefully that will work here.

[!potatoes!]

sure looks like a pumpkin. under-ripe. could be a cross, but shouldn't have come from a watermelon seed either way.

[applestar]

I'm thinking THIS is when the ol-switcheroo took place:

but it did not appear to survive the transplant at first). It came back to life in late May

I betcha the watermelon did die off and a volunteer squash which sprouted in May assumed its place.

I'm growing Kakai hulless seed squash which is used for green pepitos -- it's oblong and striped, and the stripes turn yellow-orange when mature:

In the above collage I included a couple of squash I'm growing that have deeply lobed leaves that might look somewhat like watermelon's though watermelon leaves are more blue-green, smooth, and have rounded finger-like lobes. Note though, that Kakai DOES NOT have lobed leaves. So yours is still a mystery and could very well be a bee-crossed hybrid.

Not for future reference that watermelon blossoms are small like cucumber and melon blossoms, while pumpkins and squash have those huge yellow blossoms. So that's another way to tell the difference.