The Boto-cor-de-rosa, or river dolphin, is a real animal
But the cryptid of the same name is a river dolphin that is actually a shapeshifting trickster, who will turn himself into an attractive man (often depicted wearing a fancy hat to cover the blowhole atop his head) and seduce and bang women.
That's definitely a bad idea to invite them to tea:
They know you saw them
They've got permission to enter you house
You are giving them food!!
It sound like a recipe to get your daughter stolen from you, or to have your house falling down on your head, or losing your mind or straight being skinned you and your family.
Carefully go back so they don't know you saw them.
Do not ever speak to this to anyone, not to your parent, your neighbour, your child not to your SO, not on the internet or your diary and lets hope you don't speak in your dream.
Well, I'm waiting cause "They're ugly and kill people" won't be enough. You started it, you finished. What are they named? Where are there living? How could you meet them? And how would they kill you?
That brings me back memories of when is was ~5 years old and visiting my father's cabin in the forest, which had a copy of that painting on the wall. He would put hall of the mountain king on full blast and tell troll stories just to scare me from time to time.
Nøkken was scarier though, kept me from going down to lake alone after dark, which I guess was the original intention of that creature.
When all you can see outside the window is the pitch black forest and the moon over the looming mountains in the valley, and your dad start telling you tales of dangerous troll lurking in the forest, The Hall of Mountain King got a different mood over it. Especially when your father is telling you that as the music is reaching its prestissimo finale the troll in the tale is running towards your house lol.
If any cryptid out there actually exists, my bet is on bigfoot just because it would be the most mundane, boring thing to be proven real. Just a big ape? Fuck that. I want the Dover Demon to be real because it's actually interesting.
They've (euro cryptids) have gotten nerfed over the centuries, and the especially nasty ones probably got wiped out during world War II.
Our (American) culture is strongly combative, and our last giant local war was over a century and a half ago or so. The dark things that have crawled forth from our deepest nightmares and waking dreams are far hungrier, crueller, and have had much more time to proliferate than your feeble, mischievous survivors.
Your cryptids crave petty things, like food, stealing names, or the occasional child. Ours crave the end of all things and the souls of the multitudes, to truck is into turning each hand against every other, and ultimately to drag our shattered remnants kicking and screaming into the dark places under the Earth.
Honestly the disneyification fits in pretty well with old european folklore, the gambit for a lot of our mythological creatures was tricking you into thinking they're your friends and then a whole towns worth of people vanishes. We have some wendigo stuff style too and it tends to follow a similar style of moral lesson about don't do x or you will turn into the monster or the monster will come get you.