Crabs are introduced, which can blow bubbles that are really just easy ways of getting jump attack points, and some patches of ground will collapse and give way to vertical spears, which is pretty nasty no matter how you look at it. In addition, a number of goons carry boulders and bombs, both obstacles you should avoid or take care of quickly.
You'll eventually arrive to a wall of pots; don't destroy them all, as the last few contain crabs that spring at you, and that's terrible. Afterwards, you'll come across turtles, which retreat into their shells and roll around, but they shouldn't be too frustrating. Keep on truckin' and you'll end the first scene.
Raft sequence! Much like the mine cart sequence without the high speed and inclines, you just roll around, attack the same way and sometimes drop down a waterfall, though beware of the goons as their range is elongated greatly with their oars. Also introduced are piranhas, which leap out of the water with little warning, but once you know their pattern then a simple hop on their head will sort them good.
After the piranhas, a number of geysers will show up on the path; if you stay on them just right, you can be blasted into the air and potentially land on a few heads, but due to sloppy collision detection most of the time you'll just get hurt, so I suggest simply staying away from them. You'll eventually find the mad doctor again...
Who makes an exit to give way to the giant Chinese dragon! It can rise up from anywhere and go down again, fly over the top with boulders to drop from it's claws, stop at the sides to breathe fire, spew piranhas and rocks from it's mouth, and skim across the bottom with it's head raised, requiring evasive action. Ultimately, due to the fact that it spends most of it's time moving than attacking in a method other than requiring you to bump into it, this guy is easy peasy lemon squeezy.