I'm sure there must already be a thread like this, but I couldn't find it and I'm sure that there are some hilarious stories out there!!
The first things that springs to mind for me is the year I got a new cooker and didn't read the instruction booklet properly. The turkey took 2 hours longer than expected (fortunately it had one of those cooking popper things) and DH and I were getting very drunk (this was before DS was born!!). We discovered later we had GRILLED the turkey. By the time we ate it, I was far too drunk to care!