Batman Arkham City Easter Egg - Finding Croc's Hideout and Luke's LIghtsaber

Egg 1 - Finding Croc's Lair
Most players will know that once you've defeated Ra's Al Ghul in the sewers, you can find a cage and find Killer Croc. However most people don't know how to actually get into Croc's lair.
1. Go back and line launch to where the Riddler Trophy is, use Detective Mode to find a weak floor.
2. Blow up the weak floor with Explosive Gel and you'll fall into Croc's lair.
You can actually see glimpses of something swimming in the deep water that you saw Croc jump out of earlier. Warning: If you don't let Croc out, go to his lair and then let him out, you die. I would not recommend doing that.

Egg 2 - Luke's Lightsaber
1. When completing 'Shot in the Dark', after the second/third killing you'll find a circuit box. 2.Hit the circuit box and it'll open. Inside is what appears to be a Lightsaber from Star Wars.
This is most likely a reference to Mark Hamill (voice of the Joker and Luke Skywalker in the Original Star Wars films for those that didn't know).