Create the following keys to get the gold star for this stage:

Yellow Key for baby statue
Green Key for boy statue
Blue Key for young man statue
Red Key for old man statue

Scribblenauts Remix 6-5 Cheats Hints gallery:
6-5-1-a: Unlock the statues in the correct order! Remember, Maxwell can interact with nearby objects by tapping on them!
6-5-1-b: Colored locks require appropriate keys.
6-5-1-c: Focus on the ages of the prisoners.