Advance to the Final Battle
Pause the game and hit A, B, A, B, A, left, right, up, down, and Z to warp to the final battle with Grögh.
All Items for Scientist
When you meet the scientist for the very first time, stand on the mushroom and face him. When facing him, press R, R, UP-STICK, DOWN-STICK, UP-PAD, DOWN-PAD, C-UP, C-DOWN, C-LEFT, C-RIGHT, C-UP, C-UP, C-LEFT, C-LEFT, C-RIGHT, C-RIGHT, C-UP, C-UP, C-DOWN, C-DOWN, UP-STICK, DOWN-STICK, LEFT-STICK, RIGHT-STICK, START. Then if you do it correctly in about 30-45 seconds, the scientist should say, "Impressive, you have all the items." Then he should give you all his items, the pressurized fish bowl, the pee shooter, the gliding bowtie, the helicopter hat, and so on.
Infinite lives
1-ups can be collected repeatedly, the best location to grind 1-ups is Glacier Cocktail. At the entrance, enter the small cave near the radish. Pry away the rock with your stick to find an antidote and an extra life. Enter the portal that leads to the well; nearby you'll find another small room with another extra life. Keep going back and forth between the 1-ups to gain as many lives as you need. If you have the Chameleon ability, you can also become a tomato near the large rock and the radish will toss you up to another extra life. This tactic will also work in any other area where two extra lives are located close to either side of a portal, since going through the portal resets the extra lives.