So in a corner of my yard I had a squash of some sort come up among some weeds. I believe it to be the product of a seed that must be an unintentional cross from two varieties I grew last year. (not sure which, but none were pumpkins)
What is interesting is that this squash took the form of a substantial yellow pumpkin (and grew on sprawling pumpkin-style vines.)
I plan to save the seeds from this whenever I do cut it open and plant them next year in the hope that I get something similar.