I was in one today. It was actually pretty sweet. My friends and I were going to play laser tag and we saw one across the street.
The building had the actual store logo and put up cardboard with yellow and orange bricks painted on them to make it look like the cartoon. They had everything in there (the cereal, Duff beer, and even the pink doughnuts). The manager even had the same accent as the character (I forgot his name all of a sudden) and looked similar to him.
Here's some pics I took with my phone: