We made a box cake that expired in 2007!
My oldest son graduated from college and has moved home for a few months before he ships out with the US Navy. In the boxes of kitchen stuff he brought was a chocolate torte cake mix that had expired in 2007, which means it went to school with him when he was a freshman in 2006.
Wait, it gets better.. we were jonesing for something chocolate a few days ago and decided to make the cake and see how it would turn out. While pouring the vegetable oil out of the bottle that he'd brought home with him, we noticed some little flecks of cooked whatever in the oil. "No problem", he said," it was just from cooking wontons, not fish, we always reused the oil (he and his roommates), so we poured it back in the bottle".
The cake came out of the oven looking a little lumpy, but we went ahead and mixed up the package of frosting/torte fluff that came with it, assembled the cake and put it in the fridge for later.
I tried a slice that evening, gave my son the rest of my piece after one bite, he had one the next day, and the cake has been sitting there ever since. In a family of chocolate lovers. It was bad. Yep, that bad.
Lesson learned. Stick with the fantastically wonderful chocolate mocha bundt cake that I make homemade a couple times a year, and don't try and cheat your taste buds. They know when you are trying to pull one over on them.