Wondering why Robin Williams walked onstage at Sunday's Oscars with duct tape over his mouth? Apparently, the acerbic comic had planned to perform an original song mocking conservative critic James C. Dobson's recent contention that SpongeBob was promoting a "pro-homosexual" agenda in an educational video. However, Williams dropped the act after ABC demanded some of the lyrics be changed — including a line that suggested Casper the Friendly Ghost was a member of the Ku Klux Klan. Hey, it's not like he accused the Smurfs of being Nazis.