The Audio Track Saved You.
When I first began watching, I realized the audio sounded familiar, though the credit to WKUK didn't help me out much as I don't believe I've listened to any of their other stuff. I've heard this one before though (and possibly even seen it animated by someone else).
The actual animation and drawings were uninteresting. Typical stick people a la Cyanide and Happiness. The animation was decent, but in terms of visuals, I was extremely annoyed at how you simply layered the face details onto the heads so that the blood spatter appeared the same when a character's mouth was open (instead of having an empty mouth). It didn't look polished and it would have been relatively easy to avoid.
The gun was ugly and I've seen it too many times.
I didn't feel like the lip sync was very good, but as you say - it's one of the first movies you lip synced, so by that regard you did well.
Despite having an audio track that you simply had to stick in, you actually had audio clipping issues. Considering you didn't even record the track and I guarantee there is nothing wrong with the track, you should have played around a bit to fix it considering you did something to break it.
All in all it was just OK. I feel like more effort should have been made on your end to entertain rather than relying on the audio to win your laughs.