3. スリープ Suriipu (Drowzee), スリーパー Suriipaa (Hypno), ムンナ Munna (Munna), ムシャーナ Musharna (Musharna)
These four are definitely inspired from the yokai called baku. A baku is a yokai that looks like a tapir. It devours dreams and nightmares exactly like the pokedex entries for the four Pokemon that was mentioned.
Now, the Baku could be summoned right after having a nightmare and by repeating these words: “Baku-san, come eat my dream. Baku-san, come eat my dream. Baku-san, come eat my dream” then as said in lore, it would come and eat the bad dreams ensuring a good night’s sleep. Just be careful not to summon it too much as it can also devour hopes and desires leaving an empty life.