It is not yet known what constitutes a paradoxical 'removal' of an object, but it is theorized to be any object that has already been interacted with in the present timeline, such that removing it would change the past. The eight humans could not be appearified because if they had then they could not have been around to raise their children or to play the game. The rotten pumpkin had been eaten and Jaspers was about to tell Rose a secret. Unless the Space player is dead set on capturing the frogs afterwards at the time, the frog itself is appearified rather than the paradox imprint.