You wanted a thorough critique; I'm giving you one. Any questions, respond it, and I'll respond back to your fourm post.
I almost had a hard time following the story, but at least I get it:
"Man walks on moon, man finds life, finds out alien life likes to listen music."
However, the visuals doesn't really strengthen that message across me very well.
What I would do in this case that I'd first introduce the astronaut, place his flag on the moon, and then walk around that he's finding life.
Then, instead of having that banana-alien walking, make him dancing to the music. Right now, he looks annoyed and bored to the music rather than enjoying it.
For the fade-in / out text, I recommend 3 seconds, and then fade. Longer than that makes the whole video boring already.
Artistic-wise, I'd suggest vary your line thickness on your drawings.
Walk-cycle of that alien was alright; could use work. The banana's body movement and face is jarring.