Why did God curse the serpent when Eve originally sinned?

Ok he was pissed at what he had done... but the serpent was the Devil in disguise and not a real serpent like those God created... and they say God will not condemn one for anothers fault, so why did God curse the serpent when it was the Devil, why couldn't the all mighty see that it was Satan in disguise? and leave the serpents alone? it wasn't the serpents fault the Devil used their disguise, so God is condemning a life for someone else's mistake... The Devil could have easily disguised himself as a bear, and then would have God cursed all bears? and it's not that God was cursing the Devil, he did that when he rebelled and cast him from Heaven... why would he curse the Devil twice?