There are a total of nine effects that can be found in Madoru-Mu, this page will offer a bit of info about them.
Effects
Rabbit - Isokishi gains rabbit ears and red eyes, her walking speed is increased slightly.
(It can be attained by interacting with a white rabbit in the clover section of the Giant Garden.)
Pudding - Isokishi's head becomes a pudding, this effect appears to be cosmetic only.
( Interacting with a pudding on a plate in Dessert World will give you this effect)
Mermaid - Isokishi turns into a mermaid.
Angler Fish - Isokishi's head becomes that of an Angler fish, it helps to light up dark places.
( Can be found by interacting with a small angler fish on the Ocean Floor)
Scythe - Isokishi wields a scythe, this can be used to kill NPC's
( Can be found in the grave-stone world by interacting with a bloodied scythe)
Rain Plant - Isokishi's head becomes a rain plant, when equipped; rain begins to fall.
( Found in Lilypad World, interact with the rain plant there to get it)
Surgical Mask - Isokishi wears a surgical mask, this is just a cosmetic effect.
( You can get the surgical mask by interacting with the lone nurse in the hospital area)