Actually the Michael Jackson zombie thing has been used before in other media I'm pretty sure. I seem to remember there was a bit on that in "Return Of The Living Dead Pt. 2" (I think) where the zombie hits an electric fence and starts jerking around break-dance style, and yes it looks like Michael Jackson.
I think law suits and such are an increasing problem if they prevent homages like this one, even if it never went to the court phase.
I liked Michel Jackson's early work when I was growing up, despite what he turned into. On a lot of levels I suspect this is a sign things are getting more mercenary/draconian after his demise than they were when he was alive. Sort of like how Elvis arguably became a bigger business after his death than when he was alive due to the way the estate merchandised his image and intellectual properties and such...
Even if he was a child molester, he didn't seem to be that uptight or especially touchy when it came to his work and people making homages or parodies and such. At least in this respect he'll be missed, because I think that's an attitude towards your work and doing business you just don't see much anymore.