I loved everything from the character designs to the environment designs to the animation to the coloring and so on. I loved the sound design too at the very beginning and the music.
The only few things I dislike are the following: When they exit the diner, the shot on the inside of it, they just disappear, they don't interact with the door, yeah the door rotates but it doesn't look like they're the ones doing it... it's the same thing with the outside shot, and when the smaller guy jumps in the ship there should have been just one more frame. And when the ship leaves the screen for the first time might have looked better if it went more into the camera, not entirely head on but just a little bit more.
And the last thing, if I had to nitpick I'd say you cut into different scenes a tad bit too fast, like a second too fast.
The few things I mentioned aren't too much work. Just don't be lazy, it's all I have to say, you're really talented and amazing. I'm giving it a 4.5 score but in reality it's a 4.9/5 :)