Not something stupid I've done at the moment (although there have been plenty of those!) but something stupid my husband did about thirteen years ago. The "mayonnaise on the ceiling" just brought it all back.
Just after our son was born, I was suffering from serious PPD, and my gem of a husband stepped up to the plate and offered to make his speciality, Spanish Rice-A-Roni. (Hey, at the time, anyone besides me cooking was a wonderful thing!) His version involved a can of tomatoes. I was in the kitchen marching around trying to get the baby to calm down. (Baby only was calm when whoever was holding him was on the move. Exhausting. He's an only child, needless to say...) DH was working fast, trying to get everything assembled and into the microwave because he could sense that I was just about at my limit and he wanted to take over. (Sweet guy!) He opened the can of tomatoes at breakneck speed, grabbed the can and... dropped it. It landed bottom down on the floor, and the contents rose straight upward and covered a two-foot area of our ceiling, which is as high as most ceilings are. I have to admit, it was particularly impressive-looking, this geyser of canned tomatoes going SPLAT! above his head...
Keep in mind that I had PPD. He was terrified that I was going to lose it completely. I do remember thinking for one second, "Dear God, how should I react to this?" And then... I burst out laughing. There was a hysterical tinge to it, I must admit, but I laughed, and I hadn't done that at all since the baby was born.
I never was able to get the tomato stains out of the ceiling until Mr. Clean came out with the Magic Eraser. Thank you, Mr. Clean!
(I'll 'fess up about my own stupid stuff if I can ever think of a sufficiently entertaining way of phrasing it...)