Gagaman covered it not too long ago. While Westerners received an Adventures of Sonic the Hedgehog design of Robotnik, the Japanese received the original in-game Eggman design. Since 1993, the alternate Eggman toy occasionally appeared in books (as Gagaman mentions in the above link), the Sonic 10th Birthday Pack and online. Most recently, the McDonalds Eggman appeared in an online auction at rinkya.com. The auction also includes Sonic, and both toys are unopened. The only downside, the price is set at over $50 and that doesn't even include whatever shipping is. Still, it's great to see more images of this elusive toy! After the break, check out two more images of Eggman and Sonic.
The toys in their protective baggies: