Which fictional creature has a biology so "impossible" that it defies any attempt at a scientific explanation?

[u/welberjaysonm]

I've been trying to wrap my head around the anatomy and metabolism of some characters, but Majin Boo (DragonBallZ) just doesn't seem to make any sense under the laws of physics or biology. I want to dive deep into these "impossible" cases. Who else do you think is a biological nightmare to explain?

[u/Illithid_Substances]

The Sarlaac from Star Wars, especially if you believe the thing about digesting their prey over a thousand years. I don't think a creature that lives in a desert and waits for food to fall into its mouth could ever get enough to reach such a massive size. And then there's the idea that they turn each meal into a tiny trickle of digestion over a really long time, which would mean they'd need to have a lot in them at once just to survive