I have numerous squash and melon plants. None look like this. I did not plant it there, that's where the peppers are planted. I have a few tomato plant volunteers as well, but I know exactly what they are. We had a straw bale garden last summer that when I broke up the bales I put it in the finished compost pile. I remember what kind of tomatoes but I don't remember having any thing that looks like this. I am guessing gourd or melon. A few more weeks and I should know.