Ok, so here's what I'm thinking...
While we were gone on vacation, some kid pulled Avery aside and said, "Here's the deal. You are three years old now. It's time you start acting like it."
"It's time for you to say "Why?" to every single sentence that comes out of your mom's mouth. Even if it makes no sense. Even if she is so logical, it's scary. Just do it. Over and over and over. It's your duty as a three year old."
"Another thing, since your parents dumped you here while they went on vacation, try to drive your mom crazy when they get back."
"Smear yogurt all over your hair during lunch, poop and pee yourself as much as humanly possible, dump weeds into your kiddi pool after your mom's done cleaning it, and laugh at your mom as she tries to fasten your baby brother into your high chair. And he can't even sit up yet!"
"See? It works! She's lost her mind! Isn't it fun?"