The idea is nice, the animation is awesome, the art style is superb. However, they really overdid it, and ruined the punchline by making it long and easily predictable.

If it was just a 10 second clip, with the mouse trying a few punches and kicks on the cat, followed by the cat immediately killing it, it would've been hilarious.

As it is, it's only a show of skills regarding the animation and the art style, but it's not funny at all, because anyone can see the ending coming from a mile away.