Elephant in the house

I have an elephant instead of a cat.  For something that doesn't even weigh 10 lbs, how on earth can she sound like an entire herd stampeding through my house?

Katz:  Look at me, looook at meeeee I'm super faaaast!  *throws self on bed*  HOLY CRAP THERE'S A BAG!  *proceeds to turn into KittyNeo/Nightcrawler so she can twist her body around and teleport to not land on the bag*
Bag:  ....
Katz: *stares at bag*
Bag:  ....
Katz:  *tries to eat bag*
Bag:  *RUSTLE*
Katz:  HOLY CRAP THERE'S A BAG! *goes tearing off the bed, back into the living room*
Bag:  *smug silence*
Me:  *sigh*

.2 seconds later...

Katz:  Look at me, looook at meeee....
*RUSTLE*