A Halloween special challenge

An army of little monsters are at the gates of Mathlantis, ready to sweep the streets of our beautiful city in search of candies. With the fog, Sonya finds it hard to distinguish them. Help her to see better how this army of monsters is formed so that she can prepare for the distribution of treats.

Place the pairs of monsters to the right of the image, so that each monster appears only once in each row and each column. Careful, Sonya really doesn’t see anything, there are two pairs too many.

Can you solve this puzzle before the monsters enter the city?