1. Make sure the masks don't inter-penetrate, like those at the front; 2. More varied facial expressions, perhaps (although I understand the point is that only the different one is happy/smiling, but the rest may be unhappy in more different ways); 3. Different degrees of wear and tear on the masks (this may send an additional message, BTW: the happy one has only just been discarded and doesn't yet know what it's really like - that's why it's so happy. That sort of things).
1. Make sure the masks don't inter-penetrate, like those at the front; 2. More varied facial expressions, perhaps (although I understand the point is that only the different one is happy/smiling, but the rest may be unhappy in more different ways); 3. Different degrees of wear and tear on the masks (this may send an additional message, BTW: the happy one has only just been discarded and doesn't yet know what it's really like - that's why it's so happy. That sort of things).
What material is that supposed to be?