Liu and Berlioz both do this.  They do it as they go into tunnels,
sometimes in the tunnel as they lay in wait for an unsuspecting fuzzy to
come along, and when they enter the litterbox.  Liu also plays Whirly-Bird.
He loves this, really...Really!  He's spread out on your forearm, legs
firmly wrapped and clamped.  His head is in your hand with the fingers
holding it.  You raise your arm up and down rapidly.  His tail goes like
mad.  No other ferret I know likes this, and I really don't recommend it,
as some ferrets do get motion sick.  But Liu does enjoy it.
[Posted in FML issue 2781]