My worst experience had to be 2 years ago during free dining when my parents came with us. My dad is not a good vacationer but I hadn't been on a "family vacation" with my parents since I was a young teenager, so I guess I was hoping he'd mellowed with age. I should have known better!
We were having breakfast at the Starring Rolls Cafe in MGM (as it was known then, and always will be to me), I was sitting across from Dad and my DD (then 7) was sitting next to me. DD was thrilled because the CM at the cash register had noticed her birthday button and gave her a free cupcake - for breakfast! Somehow my dad accidentally dumped his steaming hot coffee in my lap. I jumped up, screaming, "HOT! HOT! HOT!!" and Dad got mad at me (!) for making a scene. All our food was ruined, including most of DD's birthday cupcake, and my legs were blistering. They did give us new food and new coffee for Dad, but DD's cupcake was not replaced because the CM that gave it to her wasn't there any more and Dad was too embarrassed to ask for another one. (I was busy wiping off the coffee.) She did eat the part that didn't get spilled on. What a trooper!
My shirt was ruined, and of course it was a brand new white Tink shirt that I had bought just before the trip. Dad offered to buy me a new tshirt, so I went and picked one out and bought it on his room charge. When I gave him the receipt, he freaked out at the cost ($28) and wanted me to pay him back! To add insult to injury, the shirt didn't even fit and it was the biggest size the store had (2x - and I am nowhere NEAR a size 2x!) I returned the shirt and decided to do the adult thing and just pout all day in my stinky, coffee-stained shirt and burned legs. Dad also did the adult thing and stormed off to the hotel muttering about ungratefulness.
Later that same day, after Dad returned and family harmony was restored, we were in the preshow area for MuppetVision 3D. It was pouring rain outside, one of those sudden afternoon 3pm Orlando storms that seem to hit every day. I was holding DD (then 2) and suddenly felt warm. Yep - she peed on me! Without a word, I left the show and walked in the rain to the Muppet store to buy new clothes for both me and DD, then over to Pizza Planet to change us both and get some lunch.
So in the space of a few hours, I was spilled on, burned, made to feel like a fat cow, scolded in public, and peed on. Yep -- that was my worst experience. It could have been worse: the year before I broke my elbow on my first day of vacation at Universal.
FWIW, the day did get better. The CM at Pizza Planet must have noticed I was having a hard time. Not only did he carry all our food to the table for me (I was juggling the stroller and the tray) but as soon as my family joined me, he had a Magic Moments certificate made up for my older DD for her birthday, and dumped a pile of Mickey Rice Krispy treats on the table -- I think there were about 12 of them.