If the target creature is an illegal target by the time Pressure Point tries to resolve, the spell doesn't resolve. You don't draw a card. If the target is legal but doesn't become tapped (most likely because it's already tapped), you do draw a card.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.