His hand springs like a cobra while his head snaps like a rooster's. It's a work of art, that move Donald Trump uses for emphasis when he barks ''You're fired!'' on promos for NBC's hit The Apprentice. Surely he's been doing it since the go-go '80s, right? ''I didn't do it consciously, I don't do it all the time, and I didn't even know I was doing it until I saw it on television,'' the boss insists. But now, of course, he's tickled pink to think that Kelly Ripa uses the move on her morning show (''It's very cute,'' he says), and that he might have coined TV's biggest catch-gesture since Fonzie's thumbs-up. Says the Donald delightedly, ''I can't walk down the street without having people say 'You're fired!' -- always with the hand.''