Patrick has this twin thing figured out. Lilly's very much in a phase (okay, her entire life has been a phase) of wanting whatever he has, just because he has it. He's finally figured out what to do if he wants something and she goes for it. He finds another toy and starts feigning interest in that (asking her if she wants it would be too overt), then as soon as she latches onto that, he goes for what he really wants.
Smart kid. They also blame stinky diapers on each other. I'll ask who's got on, and they each instantly call out the other one. Silly silly twinsies.