The description of the Command spell says:
You speak a one-word command to a creature you can see within range. The target must succeed on a Wisdom saving throw or follow the command on its next turn […] If the target can't follow your command, the spell ends.
The rules on surprise state:
If you're surprised, you can't move or take an action on your first turn of the combat, and you can't take a reaction until that turn ends. A member of a group can be surprised even if the other members aren't.
Does a surprised creature obey the Command spell? If a surprised creature is targeted by the Command spell, what happens?
I'm unsure which effect is more specific, and therefore takes priority. I'm leaning towards Command, simply because Surprise functionally takes away a character's turn from themselves, but doesn't incapacitate them the way a Sleep spell would.
Best Answer
They follow the command if they are able to
The surprised condition prevents a creature from taking an action, moving or using a reaction until the end of their turn. Any command that requires a creature to do one of these thing will count as the target not be able to follow the command. Therefore the spell will fail. Not all command options require an action though. For example the typical commands given in the spell:
You can also give a command that isn't one of the ones listed. Anything that would not require your action or move would work, such as speaking (or not speaking) or any number of other things the player may think of. Note: you cannot use an Object Interaction, as that must be taken during an action or your movement.
If you are going to cast Command on a surprised creature, make sure it is something they can do without using their action or movement. Otherwise, it will be a waste of a spell.