Because I'm a terrible, impatient customer, I peeked at the film the day it was developed. At first glance I didn't recognize any of the places or faces I would have expected to be on the roll. Upon further investigation, I realized the roll was also double exposed. I double checked the tags on the film to be sure I wasn't just stalking someone else's film by mistake, but as I did so, I suddenly recognized one of the faces on the negatives.
Depending on what camera you use, sometimes the film doesn't get rewound all the way back into the canister when you finish shooting it. If you happen to overlook that, and stash the film to be developed later, there is a huge possibility that you'll find that film years later and send it to your mom for fun. I took the original images sometime around 2008 (I think). Considering that neither of us knew, or expected the roll to have already been shot once, some neat things came out of the accidental collaboration.