Not all bad customers are adults...
I walk up to a young couple and their three year old child. I ask if they'd like something to drink and the little girl says, "YOU DRINK PEE!!!". Her mom doesn't even acknowledge it and orders a milk for the tiny monster. I come back to take their order and the mom says to the little girl, "Now tell the lady what you want to eat." Which is always great, because kids take 10 minutes to order a hot dog. The little girl says, "I want a pony!!" To which I reply, "A little thing like you couldn't eat a whole pony. Silly girl. Did you want a cheeseburger?" The mom looks at me all evily, "She can order for herself." So, I stand their waiting while the little darling tries to stick a crayon up her nose and her mom coos "C'mon honey, tell the nice lady what you want to eat." Instead of ordering the little girl bangs her spoon on the table, throws her crayons at the busser, picks her nose. I ask the dad what he'd like to eat, while this is going on, and before he even opens his mouth, the mom says, "I would appreciate it if you would stop trying to rush my little girl and let her order." To which I reply, "I'm sure that couple [pointing to another table waiting quietly with their menus closed in the universal symbol of "ready to order"] would appreciate it if you would just order for your daughter so they can order as well. I'm sure she's capable, but right now she seems distracted, so maybe you can help her out a little bit."
Okay, I admit, it wasn't the nicest way to have handled that, but seriously, I was there for like six minutes and I had two other new tables to get to, I'd already offered to come back, tried to take the dad's order...I felt I'd ran out of polite options. My only other choice was to walk away.
The mom orders the kid a cheeseburger.
When I bring their food out, the mom asks for another milk for her daughter. I explain that I will have to charge her for the refill, but I'll gladly get her one. The mom opens her mouth to say something but the little girl starts talking first, "My mommy says you're a stupid bitch." The dad cracks up laughing, the mom turns beat red, grabs her daughter out of her high chair and runs to the bathroom with her. The dad says to just bring the refill and apologizes.
When they came back from the bathroom the mom wouldn't look at me, and the little girl was all teary eyed. Though she did throw her french fries at the bus girl.