You run around Springfield as Homer and do missions with the camera above you in a no-roof style view. The best part is just interacting with all the characters and the rooms/environments that are pulled right from the show. Very well done and awesome when you have a few minutes to kill.
Check these screens-
http://www.flickr.com/photos/15702350@N00/sets/72157600927666750/
Check these screens-
http://www.flickr.com/photos/15702350@N00/sets/72157600927666750/