These are Feves. A Feve is a ceramic (kiln fired, glazed) object that's often baked into cakes. If the feve comes out of your cake slice, it acts like a prize. While the benefits of hiding ceramics within baked goods are dubious, the figures themselves are collectible. Different cartoons & popular
characters have all appared as feves, so why should Sonic be an exception? They are often hand painted, leading to odd looking paint jobs and variances between figures. (look at how Knuckles has a green body & legs) Each base is labeled and dated, and they're all quite early, with the Sonic being from 1991. Knuckles & Motobug there are probably later figures. Burrobot & Dr Robotnik are 1992. You can tell they're stock art inspired, but they do try to get the detail going. "Feve" may translate from French as "Bean". 

• Flicky Flicky
• Tails Tails
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Here are two more feves, Tails & a Flicky bird. Tails isn't the best either, with red legs, no socks, and just shoes. He's also rather fat...but it's the super big nose face and small ears that make him almost unrecognizable. If it weren't for his 2 tails he could just be some generic animal figure. The Flicky bird is better off...but early flickies are generally depicted as being blue (with red accent beside the eye) however this one appears to be reddish or brownish all-over. (Getting a figure entirely the wrong color hadn't happened up till this one) but, at least the proportions here are a bit better. 

You can see Tails is really pretty 3d with his hand up like that. The most interesting one is Knuckles because they have him on a white pillar 'background' so there kind of is no real back-side to the figure.
Why? It's to avoid undercutting which he would create with the down spikes on the figure. It would never come out of the mold if he didn't have that. He's also the only character with such a form, so that's why he's unique like that. It's the same way with the 'sally acorn' tails having the white wedge under there. 

• Display stand photo discovered by MrCalistine Display stand photo discovered by MrCalistine
• Display stand photo discovered by MrCalistine Display stand photo discovered by MrCalistine
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This is a device for displaying the Sonic feves that you see in the close ups at the top of this page. It's a stand -card type thing with a paperboard "display crown" which is probably meant to go along the top of it to help advertise. You can see how the feves stick to black squares along the sides. The card says something in French. (If you know French, do write in, the text is available) Where would this be displayed though? Feves are meant to be baked into cakes for the Epiphany of 3 Kings (it's a religious holiday) and if you got the feve in your slice, it would bring you luck throughout the year. Look how poor Sonic's face looks from the side. It's all bent in. The flicky is completely orange while the art shows it as blue. The display crown art right next to the feves kind of reminds people that they didn't seem to be trying too hard with the paint jobs here.