Removing a ko's nightmare and leaving only good dreams. Wonder if the Marisa that received Doremy's treatment like this would ever get conceited and become a shithead with superiority complex (i.e "Maricha dreamed of scary Remi, but Remi disappeared, so Maricha must've punished it noze! Thus reality must be the same noze! Maricha is sorry for being so strong noze!").
Basically this is the opposite of what EasyV cited. While it's true that the opposite of something may not always yield the exact opposite results, seeing kos' tendency to spiral downwards to shitheadness whenever something positive happens to them (in contrast with adults that actually know where they are on the food chain), I doubt there would exist a possibility for them to NOT become a shitbag after Doremy treated its nightmare.