I just made flapjacks and put too much syrup in, they're way too chewy! :P
Worst would be...well once I made macaroni cheese and my dad added cheese that was out of date. He's awful for that. He once gave my mum some lobster tails that were 6 weeks out of date.

Edit: and once my friend came round and I made pancakes, she just sat idly by and read a book, even though she said she'd help. I think I put too much mix in at one point. :P I was eating them while cooking them and handing her half to her, too much at once. I melted a knob. My parents weren't happy.