Can you play Stupify (or spells in general) with no targets just to get the side effects like drawing a card?

Ruling: No, you cannot play spells without choosing all required targets. If a spell requires a target, you must have a legal target to play it.

Nuances:

• Spells with "up to" or "any number" language indicate optional targets and can be played without targets
• If a spell has multiple targets (like Back to Back requiring two different friendly units), you must choose all required targets to play it
• Spells still resolve even if targets become invalid after the spell is played