The Mandalorian and Grogu is full of creatures: Hutts, Anzellans, basically all the holochess pieces, and, of course, Grogu himself. But one of the most interesting creatures in the movie is the Dragonsnake, a Basilisk-esque monster who was revealed in the trailers before the movie even premiered.
You may not remember, but Star Wars fans have actually seen this alien before: a Dragonsnake is shown on Dagobah when Luke first arrives on the planet in The Empire Strikes Back. But, like most creatures who appeared in the original trilogy, the Dragonsnake actually has a long and storied history both in and out of canon.