3. Jellicent / ブルンゲル
From how the Jellicent looks, they must be inspired by the Nurarihyon. You might know the name Nurarihyon from the manga/anime Nurarihyon no Mago.
But there are three different stories of these nurarihyon.
One, is that it’s just an old man that comes to homes and act like he owns it.
Two, is that it’s the leader of all the yokai. Which is probably where the crowns on the Jellicent’s heads came from.
Third, they would “haunt” the sea by bobbing its big head up and down with the waves on or right below the water. It does nothing but annoy anyone that wants to fish it out by going further into the water. This is also probably where their jellyfish look came from and also why it is a water type Pokemon.
Though from the three stories the physical appearance of the nurarihyon is that it has a large head that is in the shape of a gourde. Looking at him again, I think the nurarihyon looks like an alien. >.>