First, you need to get to the banana crate.
An impromptu bridge over the water would be nice. You should start above the Rung. Climb up. Did the children meet the nice man already? If they are with him, you should probably talk to them first.
Call Rusty, the children form a nice line. Click on them to get past the smelly water.
Now, open the crate.
Use the correct tool. You get it when you deal with Bambina and Lotti as Middle Rufus.
The crowbar is next to the loitering Lotti. Give the crowbar to Left Rufus. As Left Rufus form the child bridge and use the crowbar to open the banana crate.