Mister's SMW run compared to itself. Repeatedly, with a different delay each time:
Probably not useful, but shows mario's motion through the levels in a new light, I think.
Location: The dark horror in the back of your mind
That's pretty cool. Almost seems like it's meant to map out the trajectories taken (actually, that could be pretty useful for run improvements).
Also, you could use just the trailing shadows to reflect just how fast Mario is (extra fun if you adapt it to other games with faster characters...)