dwts filming dancing hollywood Robert Kardashian  Cheryl Burke

Another day, another dance!

Rob Kardashian arrived at Dancing with the Stars rehearsal Thursday afternoon, just after taping a segment for Extra at The Grove in LA ... in the same rolled up pants!

Not that there was any doubt, but Rob proved that he is definitely a Kardashian by showing off his butt as he strut into the practice space. And according to fellow DWTS contestant David Arquette, his "fantastic" booty is "going to be a secret weapon."

Now that's one cool secret weapon! But please, Rob, just toss those pants out already!

Check out more pics of Rob and other DWTS stars (like a gorg Kristin Cavallari!) below.