It would be wrong to say that the Frog doesn't have a range of facial expressions - he has several. It's just that mostly they're quite visceral. And by that, I DO mean linked to his digestion: either unimpressed with input strategies, or disturbed by the output processes. And of course he has his blinding smiles.
But for the rest of the time, he's really a fairly earnest little soul, not given to wearing his emotions on his sleeve. Or so I thought. In fact, if you know how to read the Frog, it's all fairly easy.
Below is a fairly accurate representation of the facial expression of an unstimulated Frog.
And here's what happens when the Frog sees something he likes...
It's subtle, I know - but to the trained Frog-observing eye, the difference is quite noticeable!