I've listened to Curtis on WABC for the past umpteen years... Whenever I think of Curtis I can STILL hear him saying, "Yo, Lisa! What's up wid dat Shaka Zulu Dinkens?!?"
I think this is EXACTLY like you said, a tongue-in-cheek thing where his producer takes an extended holiday.
Curtis is new to WMAL in Washington, D. C. other than when he subbed for Hannity. He did sign my copy of Mark Levin's Liberty and Tyranny. He's such a flirt, I REALLY think he's kidding everyone about the firing.