Gothboy Gets Halloweened
http://www.newgrounds.com/portal/view.php?id=132418
This movie is not an animutation, but it does culminate in a musical finale that Andrew Kepple claims is animutational. Gothboy is a poorly-made web-comic that often attacks other web-comics of similar quality; which is to say that it has plenty of material to go on. The Gothboy comic was created by Belgian media design student Gilles Vandenoostende (Cholerae) and developed chiefly by himself and Kepple, with the influencial aid of others. The Gothboy website is currently offline but is being shifted to a new site (at the time of writing, April 2005).
To skip straight to the anmational sequence: Under "Scene Selection", choose "Teh Musical Finale".
The soundtrack is from The Monster Mash and the visuals do have occasional animutational references, but they are subtle and the overall style's "crappiness" may just be coincidentally anmutational, since animutations also generally have the stylistic reputation of being technically flawed as far as mainstream quality animation is concerned.
WARNING: Gothboy Gets Halloweened contains adult themes, potentially offensive "humour", and inaccurate references to All Your Base Are Belong To Us.