Before I was a mom, I never understood how these kinds of things happened.
If someone is just doing their job and watching the baby, how does he get marker all over his face. He's only 6 months old for crying out loud, it's not like he can get into the cabinets and get the markers down. What he can do, however, is play directly beneath the table where his sisters are coloring with markers (while I have an explanation for why he has marker on his face, I can't really think of a good explanation for why I let them play with markers) and just when his mommy steps from the room to help one of his older sisters, and although his mommy will only be gone from the room for 30 seconds tops, his two year old sister will undoubtedly throw her uncapped marker on the floor in his reach. When mommy enters the room and sees big sister's hands marker free, she will immediately look to the floor and see the baby happily chewing on the writing end of the marker. That's how these things happen. In a matter of seconds, always when mommy leaves the room, and always with the writing end positioned in the baby's mouth.