The duck character was named Ace Duck. He was mainly a character in the TMNT comics. As far as I know, his only appearance in the TMNT cartoon series was as a character on a TV show that the Turtles were watching (I remember Michaelangelo saying that he was watching the "Ace Duck Film Festival.") I think that was the "Attack of the Big Macc" episode. The only other way I know about him (since I'm not a big fan of the TMNT comics) is that they made an action figure of him.