Mystery Gourd

Generally, you should mark where you plant what seeds.  I put one of my nice, metal markers where I planted the first pumpkin seeds, then got lazy after that and decided not to mark up any more until something sprouted.  In the moment, you think "Oh, I'm never going to forget where I put something as big as a pumpkin/watermelon/squash."

Yep, I forgot.  For the heck of it, I planted a stray spaghetti squash seed between my kale, even though I had roasted the squash and did not expect it to sprout.  Something came up in that spot.  Now I don't remember if I had seeded pumpkin or watermelon in that same spot.  Probably.  I think so.  Maybe.

I'm going to have to wait until the plant blooms to figure it out.  Even then, the watermelon and spaghetti squash ovaries may look similar.  I don't remember what watermelon flowers look like, and this is a different variety than I grew before anyway.

It's probably a pumpkin.

The moral of the story is, mark your seed beds.