The weird part of my watermelon plant

I really don't know much about watermelon plants, but I do know that the plant I grew seemed to be like a chimera. I didn't grow it from seed and it wasn't just two different species grow up from the same spot in the ground. The stem of the plant had two main shoots growing off of it.  Growing to the left, the plant produced the most bountiful crop of watermelon I have ever grown. It was my first time ever growing watermelon so I am really not sure how much I should have expected from this thing but it gave plenty. Growing from the right, the leaves of the vine were shaped more like what you would expect from a pumpkin. It produced only two "fruits". This thing.

It is clearly a gourd of some kind. Is this normal for a watermelon vine to also have a gourd vine grow from it? When my Japanese friend who is somewhat more knowledgeable about growing things talked to me about it, she said it is normal, but most people cut that part of the vine off so everything can be focused on sweetening up the melons. She also said this thing is edible. Unfortunately, the watermelon plant met a premature end so I didn't get to wait and see if this gourd looking thing would change color or not. It is now just decoratively hanging out in our living room for the time being.