My kids (11 and 9 1/2) generally don't watch television, so they have no idea who Michael Jackson is.
Last night, we were watching ABC's program on the JFK assasination (I figured it might be semi-educational for them, and I think it actually was), and station showed one of those "tonight at 11" promos for the local news. I had the TV muted (as always during commercials), but my wife, who had strolled into the room, saw out of the corner of her eye the video of Jackson being led in handcuffs into the police station. They then showed his mugshot.
"So they arrested him, huh?" she said.
"Him?!?" my kids shouted. "That's a man?"
I still haven't figured out how to explain it to them. All I could really come up with is: "So they say. He has some real problems, though."