It's All Fun and Games

A few days ago I had the pleasure of hanging out with my little sister.  As usual we talked about very deep and serious things.  At one point she took a break from stuffing sweet potato fries in her face and looked at me with a troubled and solemn expression.  "So, you know the song Pop Goes the Weasel?" she asked.

I do know the song, so I nodded.

"Well," she went on, "I just don't understand what it MEANS.  I mean, really, WHAT DOES IT MEAN?"

Although we thoroughly analyzed the lyrics and spent a few hours discussing the philosophy of "It's all fun and games until...," we weren't quite able to connect the dots.  What do you think it means?