Your aim here is to find the Technodrome. It is found in one of the three underground passages (selected at random). The passages are short but have the toughest enemies so far. There are also two buildings in which you'll find weapons and pizza.
Use Ralph in the buildings, he one shots anything inside and has the best coverage for attacks with his sais. The center building has pizzas and a captured turtle in the basement. The top left building has scrolls on top right, boomerangs in the basement and a whole pizza in the top left. Use Ralph to kill the monsters on the bottom right and climb up the farthest left ladder that lets you go up, swing your sai several times to defeat the monsters in anticipation of their advance on you and then you can get the scrolls (Kiai). (HERE IS WHERE TO STOCK UP)
Don is used in the tunnels. The string ceiling enemies and jellyfish enemies are easy, but the pink rolly polly monster and porcupine are different stories entirely. Start with the top tunnel in the top right corner of the map, in your search for the boss, then go town to the one under it and finally the one in the far left bottom corner of the map. The boss locations are random and you must backtrack to get out of the tunnels. Avoiding your enemies here is easiast, only fighting when you have to. Patience is also a virtue here since you can wait out some of you enemies and they can dissapear off screen sometimes. Refill your turtles in the center building in between tunnels. It is vital going into the last level that you keep your turtles full and with as many kiai scrolls as you can get
BOSS is the Technodrome and it's big and mean, probably the hardest fight in the game. (Boss fight anyway) You WANT Donny or you NEED subweapons. Technodrome has 6 areas of destruction the front fork which has an electricity screen (Don is the only one who can hit it safely without getting hit without using subweapons) an escape hatch where foot soldiers come out of (and are a pain) two turrets which shoot at you, a rear fork that isn't much hardship and the eyeclops radar on top which is where the Technodrome takes damage (and deals out big damage to you if you bump into it) You can stand on the treads in this fight and sometimes the staircase block pattern in the front can deal damage. Be careful and don't lose your cool in this battle. If you have an abundance of kiai scrolls, let em fly from the far left of the screen and you can win in a minute or two. If you don't, it all comes down to Don and his range and power advantage in taking out the Technodrome. The more parts of the Technodrome you destroy, the easier it gets.