If the damage dealt by Gliscor's "Ninja Fang" attack is reduced to 0 by damage-reducing effects like Special Metal Energy or the Trainer card "Defender", does the Defending Pokemon become Paralyzed or not?
No, it does not. The Defending Pokemon can only be Paralyzed if Ninja Fang does 10 damage or more after all other affects have been evaluated.
Source: Undaunted FAQ (2010-09-09), PUI Rules Team (2010-09-09)