Another really simple one, I can never really tell what I should rate these, TBH.

There's a plus button and a minus button.
You push the plus, she gets bigger.
You push the minus, she gets smaller.
By "bigger" and "smaller", I mean the belly part of the picture gets scaled up and down and there's a shine effect that kicks in (one of the better shines from this dev, TBH).
You can click her belly to make it make balloon bouncing noises.

...That's about it.
It's not really a game and it's hard to call it interactive, it's more of a video that you can press play and rewind on, I guess.

Still, for a "video", it's sufficient.