Looks like a cross of some sort. If the teachers friend got the seeds from a pumpkin she grew more than likely it cross pollinated with some other gourd, squash or pumpkin in the garden at the time. If you wan't a true pumpkin it is best to use seeds from a store. Squash and pumpkins are very promiscuous in the garden, with the bees help of course!

wow... ok. I never thought about cross pollination. I also had yellow squash and zucchini in my garden. Is it possible that the bees cross pollinated the pumpkin flower with a yellow squash or zucchini male flower?
If so, is this a common occurance in gardens?