Lego Batman Strategy Guide 68: There She Goes Again, Free Play, Part 1
Okay, if you go to the left, you can blow up a manhole over, and use the steam to raise you to get some studs. In this area is also a dumpster that can be moved as a super strong character. You will find that a carrot 1/3 appears. I’ll tell you where to find the other two a little bit later.
There is a garage all the way to the left, and you can open it up with a lever and you can make a car. Keep it there, as it will come in handy later.
Also in this area is a fence, but make certain that you are a character who can stand on toxic waste. From there, go ahead and fix an engine, and then pull a lever. The doorway to the Second Canister will open, and you need to turn into Water Suit Robin in order to dive down and get it.
By the way, destroy all the silver cap things on the dock, and one of them will reveal Carrot two of three. Keep moving down until you destroy another silver cap thing, and carrot three of three will appear. So will the Third Canister.
There is one building that you can do to by using a magnet wall, then jumping to a ledge. You can form a batrope there that will allow you to take your characters to the top. There will be a heart window here, so turn into a female character to charm a guy to open nearby garage. Here you will find the Fourth Canister, so go ahead and snatch it up.
In one alley, there is a dumpster that a super strong character can move. When it is moved, there will be a garage door that nothing, not even a bomb, can budge. However, if you go all the way to the left, where the aforementioned car is, you can drive the car right up to the garage. It will open up, and when you drive it inside, the Fifth Canister will appear to where you moved the dumpster. You should be able to become a high jumper character and get it.
In the right corner by the water, there is a box that you can stand on and jump to the other side, where you can blow up some stuff with an explosive. From that, you can build a lever, and this should open up a door under water so you can get the Sixth Canister.