There's a strange, Lovecraftian terror afoot any time a child is sat next to you for what you know is going to be any length of time. And you must be stalwart in your resolve to fully ignore this child, or else. Because the moment you forget yourself and the 12-year-old turns to you and says something, anything -- even the most innocuous bullshit like "I'm going to LA" on a flight to LA, where we can all safely assume everyone is going to LA -- and you acknowledge you are able to hear the child's voice or even sense the vibrations it makes when it attempts communication, you're screwed.
Acknowledging a child is, to a child, opening your arms Willy-Wonka-wide and inviting that child into your world of magic and wonder. You have just granted access to yourself and every dusty corner of your psyche for the remainder of your time together. No subject will be off-limits, no body language will be properly interpreted, and not even things like "Welp, I'm going to sleep now" or "Welp, I'm going to OD on heroin now" will prevent the child from continuing their mad conquest of your personal space and time.
"I'm coming with you. We will never be apart again."