Normal Monsters are often called Vanilla Monsters, as a reference to their pale yellow background and how they are "plain" with no effects.
Though they do not have effects, there are often Spell, Trap, or Effect Monster effects associated with specific Normal Monsters. For example, "Dark Magic Attack" can only be used with "Dark Magician", Huge Revolution can only be activated with 3 specific normal monsters on the field, and "X-Head Cannon", "V-Tiger Jet"and "Dark Blade" are the only legal targets for “Y-Dragon Head”, “W-Wing Catapult”, and “Pitch Dark Dragon” (Or “Kiryu”), respectively.