This Articulated Creeper from Minecraft requires no assembly and very fun to play with.

To get the parts moving, it might require some force and in order to separate the legs insert a thin object in between them and carefully use leverage to get them apart. 

• 0.2mm layer height
• might need a brim if you have poor bed adhesion
• no supports
• don't print too cold or the legs on top might get loose and ruin the print
• use 5 parameters to ensure strength of the joints