first off, the penguin lair and trap seems a little easy to overcome so i came up with a rough idea to hopefully make it more interesting...
besides giving the penguin the umbrella perhaps the penguin gives Roger a riddle (kinda like the Ridler as another Batman reference). It could involve the little penguins in a choice game.
once past the penguin, the next room is the trap scene...
Roger steps on a plate on the ground where a cage drops on top of him. Penguin enters and says something like "you really think i'll let you go that easily?" He then smacks the sewer wall which opens and reveals a control panel with a lever and holds onto it. There's also a left to right switch (which is switched to the right). Once the lever is pulled, a big vent over Roger will drop a big load of goo onto him, so Roger must act fast if he doesnt want a nasty death.
The aim is for Roger to throw the smarm can at the switch so it flicks to the left. The idea of this is so the the big vent above Roger (which is unseen) will move to the left over the penguin. However, this cant be done so easily, and it must involve talking to the penguin. The Penguin will ask Roger for any last words before he dies. Roger will naturally say "yeah, what does all this have to do with the plot?". But eventually we want Roger to ask Penguin a question he cant resist to answer so that he will yap and yap about how he's the ruler of the underworld. Roger must throw the can at the moment when Penguin is deep in his speech and have his head turned away from Rogers site. If he does it when Penguin sees, he will immediately throw the switch and the narrator will tell you that timing is everything.
So after Roger successfully knocks the switch to the left when Penguin isnt looking, the Penguin will think Roger was throwing the can at him and then furiously yanks on the lever. The penguin looks up, yelps, pulls his little umbrella over his head and watches the goo demolish him.
Now Roger will be stuck, perhaps one of the little penguins who come to carry Penguins body away will walk toward the cage or the panel, look at Roger and say "thanks buddy" and kick the cage/panel which will then release Roger.
)
