My mom made creamed tuna once, and even though she's normally an excellent cook, I think she kind of had a brain fart that day and used tablespoons of salt instead of teaspoons. We happily ladled it onto our toast, collectively took a bite, and collectively spit the bites back onto our plates. Someone had the bright idea to feed what was left to our dog, because dogs will eat anything, right? No... our poor dog took a sniff, put her tail between her legs, and crawled under the porch.
My sister-in-law decided she'd try to make muffin tops when everyone came over for some holiday or another. She didn't realize that there's a special tin that you make them in, so she just put dollops of muffin batter on a cookie sheet. Muffin batter is runny but not so thin that it will go everywhere immediately... within a few minutes of putting it in the oven, she just had a sheet full of muffin goo that was dripping off the edges and burning in the bottom of the oven.
The first year I made Thanksgiving dinner by myself was a few months after I'd gotten married, and I got to use our lovely new knife set. I was happily chopping celery for the stuffing and realized something was wrong when the sound went from "chop chop chop chop" to "thhhkkkk." Luckily the knife was so sharp that when it went through those few millimeters of fingertip it kind of cauterized it so I made it to the sink before I bled all over the stuffing. Sadly, I didn't learn right away and ended up doing that two more times with various vegetables. I'm pretty good about using "kitten paws" when I chop stuff nowadays.