What I mean is, like on your standard smiley, it's got those two spots where the black mouth curve is "broken" by your next darker color. It's a valid means of AA, but I think the difference in color is so great it just looks jagged. Lightening the outline color to a not-black and/or using a darker color to break it will look better, as I see it.
If I'm still not making any sense, don't be afraid to let me know!
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