up the auntie
Refers to where a child pits one adult-relative against another in an attempt to get what he wants. A clever way for the child to avoid resorting to temper-tantrums, but equally invalid and shamelessly manipulative.
If my mom won't let me have a certain toy or candy at the store, I just "up the auntie" by reminding her how her child-pampering sister always buys me stuff I want when I'm out shopping with her.