arkham city easter eggs

in  arkham city there are easter eggs every where. Like for example on the '' ice berg lounge'' challenge map you see killer croc and penguin just sitting there. And on one of the joker challenge map outside the fence jokers sitting in a chair enjoying the show. And when you finish beating Ra's Al Goul on the way out of the sewers you get one chance to see killer croc. And the last one of the day scarecrows secret room. the location is simple.There is a boat near the gotham docks and take out your hacker at the end of the boat and theres a dead thug in there.