Need verification, sliding "player ragdolls"? player controlled radgdolls?

Well, i was JUST playing GMod, and one of the players said he “died”, but he had actually ragdolled. Like some kind of noclip mode, but ragdoll mode…
Weird thing was, he could slide around! He pushed W and slid forward, and could control his sliding around like he was walking.

Now, i need verification: is this a bug, or an actual feature?
And how do you activate it?

Sounds dumb, but it was hilarious watching him slide around the map…

More like an addon.

More like ragmod http://www.facepunch.com/showthread.php?t=718151

Sounds like that Superman mod, but you need to be dead for it to work.

Or parachute mod.

EDIT:

As in press - shift and you’re a move-able ragdoll, shift again to activate.

That’s exactly what it is.