෴Temporary Truce෴

Dream, Guardian of Positivity, the admit of Kindness and ones Happiness.
Nightmare, Guardian of Negativity, the admit of Sadness and ones Anger.

Both have an switch of personalities as Science Sans throws a mysterious potion during them fighting, after the battle and going to sleep both personalities shifted to be the exact opposite.

Dream, Guardian of Positivity, now admitting Hatred and Anger.
Nightmare, Guardian of Negativity, now admitted Cowardness and Joy.

What will Nightmare's Gang and the Star Sanses do to the sudden swap?
[PS; This will mainly focus on Nightmare.]