After the G. feeding P. the peanuts (actually, it was carrot pieces!) the other week I've been extra vigilant in watching them together. Then last week I saw G. put something near P.'s mouth. I walked over to take a look and while trying to get my finger in P.'s mouth I accidentally plugged her nostrils and out popped a GRAPE.
See picture of P. and offending grape below.
Mugshot of the carrot/grape feeding culprit.