The Green Explorer is excitable, and seems to be very adventurous. His dialogue purveys that he has explored the Land of the Purple Giant.
You’ll find the Green Explorer on the far left side of the Poptropica Towers scene. When prompted, he will tell you that you would never believe the things he’s seen in the clouds. This may purvey that he stole the Golden Egg from the Purple Giant and hid it in the Dark Room - similar to the fairytale, Jack and the Beanstalk.
Green Explorer is presumed to have stolen the golden egg from the Purple Giant.