Hypno is known as the Hypnosis Pokemon. It evolves from Drowzee from level 26. One of its moves is Hypnosis. Hypno puts its victims to sleep and feeds on their dreams. In Creepypasta lore, Hypno is the main antagonist of the song Hypno's Lullaby. The Creepypasta was most likely inspired by a Pokedex entry that mentioned that a Hypno tried to kidnap a child it hypnotized.
In Hypno's Lullaby
Hypno appears in the song by manipulating some children to follow it promising them protection and tons of fun. During the middle of the song, it ties the children up and claims that the ropes will hold them tight. This was a lie, however. Hypno then proclaims to the children that they weren't clever, and now they would stay with it forever. It is unknown what became of the children after their disappearances, but it's assumed that Hypno killed them.
Come little children, come with me
Safe and happy you will be
Away from home, now let us run
With Hypno, you'll have lots of fun
Oh, little children, please don't cry
Hypno wouldn't hurt a fly
Be free to frolic, be free to play
Come with me to my cave to stay
Oh, little children, please don't squirm
These ropes I know will hold you firm
Now, look to me the pendant calls
Back and forth your eye lids fall
Oh, little children, you cannot leave
For you your families will grieve
Minds unravelling at the seems, allowing me to haunt their dreams
Do not wail and do not weep, it's time for you to go to sleep
Little children, you were not clever
Now you'll stay with me forever.