What Am I?

Mouse, horse, swine, and dog

Came across a figure sunk in the bog.

"Alas!" Neighed horse, “I believe it has fur.”

“Nonsense,” grunted pig, “A mossy rock as it were.”

"A rock?" Pipped mouse, "A mountain more so."

And dog only sniffed, the stench making him groan.

"Well, I know I’m right," horse said with a whinny,

"Egads!" Shouted pig, “No, you’re the ninny!”

"Hey!" retorted mouse, "I saw the thing first”

"You're all wrong," dog barked, “Your brains are burst.”

The four continued walking, bickering into the night

Because who cares what it is, as long as you're right.