Bizarre concept, and fiendish gameplay will probably leave you frustrated
The controls were slow and unresponsive even for a NES game. Everything seemed to kill you, touching any obstacle that wasn't the floor, even the floor if you fell more than about 3 cm, everything underwater.
The concept was an odd one. You have an alien friend who changes shape when you feed it different flavour jelly beans. Licorice = ladder, tangerine = trampoline, Cinnamon = blow torch. You could also make him catch up by throwing a "Ketchup" (Geddit?) bean, although he would never eat these. You had to get him back to his planet by searching the sewers for treasure. Then you could buy vitamins for your vitamin gun and blast the evil sweets inhabiting his plant.
On his planet if you touched anything naturally you died, but also if the popcorn touched the floor it was game over. And how come popcorn kills you but eating jellybeans for 6 hours is ok? MGS2 plot made more sense than this. I forget how (or if) it ended, because I'm not sure I ever got that far. You died constantly! and you could blast off to his planet almost immediately with a rhubarb bean, so I don't even think you had to spend hours getting treasure to get the gun.
The only thing I can recommend about this game is that the music changed and had set ad-libs for every transformation you did. So when you whistled and he changed back from a ladder the music would be subtly different. And I am told reliably by my mum that, although this is cute the first time, if you aren't playing, the 100th time you just want to break the TV.
This game is about to be re released on the Wii. Hopefully they will make it easier, as it was way too hard for a kid to play. If they had given you a health bar instead of porcelain legs and 2 lives it would have been doable. As it is, if they release this on VC, DON'T buy it, it is terrible.