Minifig rotatable legs on a stick - what is this? What kind of piece is this? Emboss says "(c)2003 The LEGO Group" and there is a 4303 number below. I browsed Peeron a little but didn't find anything similar.

There are two red handles, one rotates minifig legs back and forth, second one make it straight.

EDIT: fixed part number, it is 4303, small chance for 1303 with overburned 1
The part in question shows up as a "Minifig Gravity Stunt Handle" (part number x817) on Peeron and a "Turntable Spinning with Sports Trick Handle" (item number bb128) on BrickLink. Looks like it appears in two sets:


Snowboard Super Pipe:


Skateboard Vert Park Challenge: