This micro plush is actually a keychain!
This Amy seems to be even smaller than the previous very little plush Amy. She's in her classic Sonic CD clothing, which is farily well detailed despite being totally tiny. They clearly put in an effort for this keychain, it's rather too bad that it is so rare. (the smaller something is, the easier it is to lose, I guess) Photo provided by: Rhia.
Tiny Tails at right is likely from the same set. He is different from the one seen on Japan Keychains 1...and yes he does have ears. They're just folded back onto his head and the photo is poor (as they didn't stand them up so he could look normal) Again, they've minded most of the details, even getting the bands on his socks in despite the size. His body is a tad big, but the whole thing is likely under 5 inches anyway. As you can see here, AnimeMate.com took the photo so they might have gotten a hold of a few of these in 2009, which may mean a chance to pick one up despite it not being common. 

If there's mini Amy & Tails, you know Mini Sonic had to exist too. Here's the tiny plush keychain version of Sonic. Like the others, he's pretty good too despite the tiny size. His shoes may be a bit big and have no buckles, but it still does look very Sonic-like. The spikes are likely to be flat fabric strips, like the figure's hands are in each of these mini keychains. AnimeMate got a hold of this one as well, but it is not common.