That whole grass is greener mentality is innate. I'm certain of it. A few mornings a week, I watch the neighbor's little girl in addition to Miss Bug (anonymity is key in online writing). Now they're both able to run all about the house and communicate pretty effectively, they entertain one another. Scratch that. They entertain me.
One of my favorite scenarios I get to witness every visit is the trading of the sippy cups. You may not be aware of this, but spill-proof cups, much like all products available at Target, come in an array of models. One child has a traditional sippy cup, the sort with two handles and a lid that requires the user to tip it back for a drink, and the other has a straw of the bite-down-and-then-sip type, like a CamelPack. Each girl proficiently uses her own cup, but, when taking a milk break together, neither is content to drink her own milk. They trade. Every time. Funny part? Neither girl can use the other's cup. So there they sit, frustrated to the point of fussiness, unable to drink, and refusing to take back their original cups. It's a phenomenon they will undoubtedly repeat with ill-fitting but cute shoes belonging to their roommates. An oddity I've come to realize as a fact. It's just plain female.