My Little Milkman

So, last night, we had gotten home from a day out. Papa Bear cut Baby Bear's hair, and I gave him a bath. I put fresh diaper and PJs on him, and gave him his milk cup. He was watching a little Barney and dancing around giggling. I was at the computer. Papa Bear was in the back and Brother Bear was in his room.

I hear this little maraca-sounding noise, for quite awhile, and a lot of silliness and giggling. Then, I looked over (like 5 minutes later), and see this:

...along with milk all over the carpet, the entertainment center, and even on the TV. Baby Bear has figured out how to bite hard enough on his sippy cup lid (a soft lid), to disengage the "spill-proof" widget that's inside. And he loves that shaking noise, so was shaking the cup, and in the meantime shaking milk all over himself and everything else. Needless to say, I was NOT thrilled with him, and even fussed loudly at him, which in turn, made him cry. That's why he's not giggling in the picture above.

What's a Mama Bear to do?