I'm looking at siffrin faces trying to see what separates out his happy faces from his fake faces...
Here's S_fake_1 (left) versus S_happy_1 (right)
It looks like both have a mouth smile and raised eyebrows. The fake one has the eye shut/curving up though, while the real smile has the eyes more relaxed. I would say this is their more relaxed natural smile. It's pretty close to the fake smile, but the eye isn't closed.
They do close their eyes in a couple other happy sprites though!
Look at those happy siffrins!! This is US_happyy_1 (left) and US_yahoo_3 (right)!
both of these have closed eyes, but the eyebrows are scrunched down and sif has an open mouthed smile! Plus the extra lines below show their eyes are a little more scrunched, while the fake sprite is really smooth! And considering part of a smile is the cheek muscles scrunching up the eyes, that shows the fake smile doesn't really have that aspect of it, just the shut eyes and a small smile on his mouth! These are very happy siffrins and/or siffrins that are laughing at something :D
