If you are Stunned, your movement isn't reduced to 0 (unlike grappled.) Can you stand up from prone while Stunned? Can you also drop prone from standing?
- A stunned creature is incapacitated (see the condition), can’t move, and can speak only falteringly.
- The creature automatically fails Strength and Dexterity Saving Throws.
- Attack rolls against the creature have advantage.
How about with Paralysed? (Identical, except with the additional clause:
- Any Attack that hits the creature is a critical hit if the attacker is within 5 feet of the creature.
In other questions, the bonus damage on Booming Blade on movement doesn't occur on a target standing up from prone, which suggests that standing doesn't count as moving. See Does standing up from prone trigger the secondary damage from the Booming Blade cantrip?