I love the animation of this! That part is definitely shining. So is the color palette and the humor, it's great.
A few things I'd like to see improvement on: Editing. Some shots just hold too long. The shot of the "Nite" reading the tablet? Too long. We can do with at least one less pass of his eyes going over the text, maybe even two. We understand everything we need to about that shot very quickly. It also holds too long at the end. Same with the shot of the nite looking back at the skeleton toward the end. This holds far too long, and the shot that slowly zooms out is also just way too long. Make things a bit snappier. I don't necessarily need, or even want, traditional Hollywood cut-cut-cut style editing, but I think there's no reason to hold any shot longer than the average audience member needs to gather all of the necessary information.
Second, I like what you're doing with sound, but I want you to push it even just a bit further! First off, all of it sounded just a bit low quality. Are you doing all of your sound in Flash itself? If so, I would recommend doing your sound design and mixing outside of it, maybe in Premiere if you've got it. And also, I just want the sound design to be pushed a bit further. More sounds that tell the story, and give us an idea of what is going on in the character's mind. More sounds that tie into the editing, more sounds that give the world a little more flesh!
Lastly, I want to address your shots. I like what you're doing generally with the shot choices, BUT, I think they could get even stronger with more practice! I want to see a wider variety of close ups and wide shots. AND, I want more shots that contain important information in the frame! I like the backgrounds you've got, they're great. But I think that sometimes, they could contain more information to help the story along, or just to flesh out the world. Sometimes it feels like there is just a bit too much dead space in the frame that isn't doing all that much to add to the film. I think more variation in lighting could help too. That cave/tunnel was honestly too bright! It could be darker and moodier. More harsh shadows. More contrast!
I'm only saying these things because I think you're very good, by the way. Don't take these negatively! I just think that giving some thought about things you could add or vary more could help these animations take even another step down the road of polish and perfection.
Feel free to disregard everything, of course, if you want, and keep making what you enjoy making! That's what matters after all.