Not The Best Send-off piece...
Things that I liked about the flash: first and foremost, if you were indeed setting out for shock value, you hit the ball out of the park on that one. You could say the ending was somewhat telegraphed, but it still is an ending that slaps you in the face.
The song is performed in a way that the transition between the adult lyrics and the kid lyrics is fairly seamless. The easy way out would have been to over-exaggerate the adult lyrics. This shows a good sense of comic timing.
Things I didn't like: the animation seemed herky-jerky at times, where it feels too much like a flash animation from 2004 instead of 2010. The material... well, the kids host with a dark side has been done before. While the joke was told well, it wasn't a particularly new way of telling it. And I didn't care for the shock ending, even if it was done well. That seems to be the only reason for this piece to have been made, is to shock with the ending.
The last piece of yours I viewed, "Prostitute Mickey 4," treated the characters very effectively. When Mickey breaks down near the end, I actually felt bad for him. That's effective storytelling. In this flash, there's no attempt made to get the viewer to sympathize with the character. You could have just cut out the song and gone straight for the ending and the result would have been the same.
I've come to expect early Peter Jackson-ish dark humor from your pieces. This isn't your best use of dark humor. Dark humor and shock works best when there is context and strong character portrayal, which this piece lacked. As a scene in a larger piece of work, this could work. But as a stand-alone piece, it's too much of an old joke before a quick and exploitative punch line.
Keep incorporating one element that makes your dark sense of humor hit home: your ability to make characters that aren't so one-dimensional and predictable.