Mesh Changes Shape when Parenting Armature My low poly character's chest and arms changes shape when parenting armature with automatic weights.
I don't know what is going on and here is the file. Just simply parent armature to cube(modified into low poly character). Link

But when I parent the armature,

This happens. Please help.
First thing, bend a bit the elbow in Edit mode so that Blender knows in what direction the arm is supposed to bend:

Now correct the IK Pole Angle value, for example the correct value for left arm is -90°: