When you go to a health screening and it's not until you get home that you realize that you have breastmilk spit-up on your shoulder and one side of your nursing bra is unsnapped.
Or when you start making lunch and your 3 year old comes down the stairs, sans pants, asking you to wipe his butt. You grab the wipes and realize he's covered in poo. A bath is necessary so you take him upstairs to the tub and you find his poopy underwear in his room, poop smears on the hardwood floor, on his freshly laundered comforter, on a towel and smeared all. over. the. toilet.
Or when you are rushed out of the shower because the baby is hungry and it's not until the next morning that you realize in your haste to get dressed, you put your underwear on inside-out.