Here's a Happy Meal McDonalds' box from...somewhere. It's likely to have been released in the UK, but if they got it, it's likely some other places did too. Did this come with a toy? If so, which set? The art here is obviously Sonic Adventure 1-centric, so you can get a good guess at the release. The box front with blue line-screen and Sega word is actually pretty stylish--a welcome change for this sort of thing. What is the side panel? "Decorate your Pens". Was the prize inside a pen? It doesn't matter with these punch-out tabs, you can make any pen a Sonic pen.

By poking along the dotted line, you can get those disks out of the box on their little tabs. The tab folds around the pen, and you have to tape it shut, forming a type of little round flag. Then, you can fill in the missing letters of the characters' names on the box. However, all of that is really obvious. (the directions at the bottom which you can't read in the photo, say the same)