This idea is based off of something you can get on another adoptable site, called Project Nyoka! The basic idea is that every time you look at a view page for any hatchling/egg that isn't your own, there is a tiny tiny chance you'll receive a special dragon.
I understand the difference in clicking between the two sites, so I think this "special dragon" would have to have a very very very small chance of getting (maybe around 2 - 4 percent). Also, if you receive one, it would already be an adult or act as a frozen hatchie (similar to a leetle tree) that way you avoid users possibly getting one while they're locked and can't take eggs.
You can receive more than one of these special dragons as well.
I think this idea works better than a badge, because with a badge, you could only get one, whereas with a dragon, users could see the difference in how much that person clicks. Like, if a user has one special dragon, you would know they click a lot. If a user has, oh lets say, 10, you would know that they click A LOT of dragons.
Another idea would be different colored sprites, but I don't really know how that would play into this...
As for the actual sprite and design of this dragon itself, that would be totally up to someone else (I can't do that stuff! Haha!)
Other suggestions, anyone? I think this would be cool~