I think these smileys are so neat that it's hard to defend not copying them

It's square, tilted yellow faces. Most smileys are yellow and if you're making them square then tilting them is a requirement to make them interesting and not totally boring.
So it's not impossible to get the idea on your own, even if he saw them here, what's the big deal with liking them enough to make something similar?
Besides, these one seem lower res and seem to have a bit of curving to them.
If you compare them side to side you'll see that they're not too similar.