I like it.
Somethings that I would change would be their voices in the first part. I get what you were trying to do, but it sounded too weird, like their voices were slowed down and a bit deeper. I believe it should have sounded maybe muffled, or just more far away, but not quieter.
Animation needs a lot of work, maybe use more camera angles on different perspectives. I would also recommend making more face expressions, to give the animation more "life".
Use references when drawing, it'll help you get the proportions right.
And well, have to say it, when he started singing the little mermaid I burst out laughing XD
Man, I love Game Grumps.

Not bad:
Auditory: 4/5, Fairly funny (at least to me), but perhaps a bit on the overly silly side. A clever joke or two wouldn´t have hurt, although I might be missing the point.
Visual: 2/5, At present, animation is very unspectacular. While I understand that it might be difficult to animate well, only the end result matters. To be honest, this is still better than what I have done, but I do not presume myself Newgrounds worthy.
Overall: 3/5

I kinda like this, but really, that's mostly due to the funny audio. There wasn't very much added to what was already there, as in it wasn't visually interesting (although I do like the colours used). It seems like you've got the right intentions, but you should choose an audio clip that has the Grumps playing out or describing a scenario, that way you can add the visuals yourself, making it more interesting for the viewer, rather than just having Arin sitting on the couch, with an occasional background change.
You're headed in the right direction though, so keep it up! :)

The audio is off during the first scene, and there is a lack of actual animation(s). It's just a song by Arin with a few drawings.

Credit where credit is due, you did a good job dealing with such a random audio clip!