HALF MOON BAY, California: He was a Northern California resident in his 40s who had been a science student in the Midwest. And he was always sending packages wired up with batteries. In short, Tickle Me Elmo designer Mark Johnson-Williams was exactly the sort of guy the FBI was looking for in the Unabomber case. Johnson-Williams says the Federal agents looking for the Unabomber investigated him for six months. "I was always sending batteries and headless dolls in the mail. I think that's what caught their attention." No word on whether agents confiscated any of the popular Sesame Street dolls during their probe.