Shiny Happy Monsters

The Five Creepiest Cameos in Sesame Street History (spin.com).

I don't know about creepy. Odd perhaps, but not creepy. I was reminiscing with MJ about other performances; he remembers Stevie Wonder jamming on "Superstition" once, and it being awesome. I distinctly remember James Taylor singing "Up On the Roof", too.

Are there any that stand out in your brains?