The Smurfs 2 is my idea for the sequel to The Smurfs. It is told in greater detail in blog posts on Smurfs Wiki, starting with this one.
In Smurf Village, everything is going good. Smurfette is being beautiful, Police Smurf is giving out tickets, and Papa Smurf is making potions. But meanwhile, Hogatha discovers that a magical amulet, the Amulet of Power, is hidden somewhere, and since she has a magic map which gives her directions one step at a time. She decides to check it out and destroy some Smurfs while she's at it. So she goes on this journey, and drags along her reluctant assistant Helen - literally!
Meanwhile, Papa Smurf sees in a magic potion that the amulet is in New York, and he sets up a trip to get it before Gargamel, who is in New York does, and he finishes doing this just before Hogatha visits Smurf Village and sends them running to the forbidden cave where the blue moon portal appears. It's not a blue moon, but Papa Smurf knows the spell, and Hogatha has to wait there cause the map says to.
His plan is to activate the portal once she gives up and leaves, but Police Smurf is captured by Cannibal Smurf, who must be rescued before he gets eaten. Cannibal Smurf and his buddies chase the Smurfs away back to their camp, and Hogatha sees them and goes after them. Papa Smurf has to activate the blue moon in order to escape from both Hogatha and the cannibals. The rest has not yet been written.