Yup. A 20A 120V plug has the neutral prong rotated 90 degrees to prevent it being plugged into a 15A outlet. 20A circuits usually get outlets with a T-shaped neutral slot to accommodate both plugs. So far I've only seen 20A plugs on server rack PDUs and some especially large wall A/C units.
If you think about it, being able to deliver 240 volts for large appliances, while still having no point in the system be more than 120 volts above ground, is actually pretty clever. It has the effect of reducing the shock hazard, even though it wasn't originally planned with that in mind.
Biting the hand that feeds IT
