I have one that likes to stare at me and one that likes to stare at one of my other pokemon but they've never been aggressive. [ the one that stares at him is right behind him actually, staring. say hi to Yoonjae the Xatu. ]

As for the stolen things...if you explain yourself it should be fine, I think. I haven't had that problem but I know some pokemon are prone to that kind of behaviour.