Blue rat?
 

I was just traveling to snow when i spotted a blue rat with a fuse tail , I do have some pictures but i don't know how to post them

You must be colourblind child

I've seen that rat before. Careful, they explode.

As dusty has said in the past, all the baddies who spawn in the railroads have a "rare version" similar to shiny pokemon.

Black slime-fire slime
Rat-bomb rat
Bandits-bandit leader
(sorry i'm not aware about the bat one, i believe it's skull bat)

I have a picture of the Bandit Leader. I didn't know there were other rare baddies, though.

I ran like a girl towards the fire slime

No the skulls bats are the common ones now i thought