The golden I used to have did similar things w/her ears/eyes when I approached w/a leash. It was a habit formed from years of me sliding a new collar on with the leash attached. She'd squint and pull her ears back in anticipation of the collar being slid over her head.
The smile? I never got that.
The dog didn't die. He survived. The little dog pulled him to the side of the HWY and the firemen came.
At least that was what was in the first report! Sorry.
If it's commercially made chocolate, they'd have to eat a lot to get sick. If it's 'real' chocolate, a little amount can be sufficient to really make them sick. Commercial chocolate is a lot of fake stuff.