You've seen this doll elsewhere on Japan Plushes, but this one is slightly different. It's their usual 'big size' Sonic plush, but the paper hang-tag is different. He has been re-tagged with Sega's "Mobile Items" tag. It just has a CG Sonic picture, but they've got him reaching toward a mobile phone to illustrate that it's for their mobile division. Dolls like this with the new tag were given away at the Sega Mobile Sonic Celebration event in Japan, which was around June 30th of 2008.
This event was reported on by Japan's The Sonic Channel, which is also what took a picture of the doll (w/water bottle for scale)