Very nice! Especially when you didn't even use a tablet for that. As far as how "correct" the body shape and everything is... well, I don't feel like I should be one to give comments because I haven't mastered that myself, LOL. Tbh, I think what you need is a tablet!
I really love your colours, and you draw pretty good hands (much better than what I can do.. mitten hands ftw). At first thought, I thought your eyes might've been a bit big (come to think of it, my first drawing also had overly huge eyes too xD) but I don't think that's the case since I've seen some really nice drawings with huge eyes as well. Maybe it's because only the eyes are "outlined" with black, that's why it stands out so much more from the rest of the picture. Maybe you could try dark brown-ish lines next time if you didn't outline the rest of your pic (not sure how that'll look.. but I think I've seen some nice pics with brownish outline)... or maybe you can just add some outlining to the rest of the pic XD But I can imagine how hard outlining would be for a MOUSE.
But anyway that's really good... with a mouse!! I MEAN A MOUSE!! I'm sure you'll make awesome work once you get a tablet.
I also actually really like the style/colour/overall look of
this artwork of yours, btw. xD I'm gonna comment all over your devart tomorrow as I have to pop off right now, very nice work!!