Bronze:

Good start!
Objective: Complete the first level

First golden nugget
Objective: Complete a level by beating the Voodoo time

Creeper weaver
Objective: Complete all the World 1 levels

Baobab tree climber
Objective: Complete all the World 2 levels

Coconut juggler
Objective: Complete all the World 3 levels

Temple looter
Objective: Complete all the World 4 levels

King of the jungle
Objective: Complete all the World 1 levels by beating the Voodoo time

Prince of the desert
Objective: Complete all the World 2 levels by beating the Voodoo time

Champion of the tropics
Objective: Complete all the World 3 levels by beating the Voodoo time

Silver:

Lord of the dungeon
Objective: Complete all the World 4 levels by beating the Voodoo time

New skin
Objective: Change your appearance before selecting a world

Gold:

Voodoo sorcerer
Objective: Complete all the levels in each world by beating the Voodoo time