These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Demonic Turtles: Turtles divebomb you from out of nowhere and do massive damage if they hit you.
That One Boss: Really, any boss in the game, but the Joker is especially difficult if you don't have the right character build or the right weapon.
The Untwist: The Baku, a japanese spirit who devours dreams and nightmares, is usually depicted as a tapir. You remember Drowzee from Pokémon, don't you? Yeah, the Tapir is the game's villain.