Not very funny.
I really liked the art and animation. The difference in the drawing styles was great and made the whole thing much more interesting.
Sadly (and this is the part that will probably make a lot of people dislike my review), it wasn't very funny and the voice acting was pretty awful.
First of all, random != funny. Most of the jokes were either nonexistant (some random person blowing up isn't a joke, per se, unless it is ironic or came after foreshadowing), or simply not all that funny because the timing wasn't very good. Timing make a good joke great. I will give you props for not using a single swear word. Cursing is also not automatically funny despite what so many people seem to think.
Also, I'm sorry to say the voice acting was just terrible. Pretty much all the male characters sounded extremely similar. The females all sounded different enough to make me think they were perhaps different people, but the acting itself was really lacking.
Now don't get me wrong. I give credit for the work involved in creating this movie and I understand how hard it is to voice act and come up with truly funny jokes. It simply falls short in my book and would not have made it to the front page.