In MtG, when casting Curfew, what happens if caster does does not have any creatures? Does spell still work?

Question

In MtG, when casting Curfew, what happens if caster does does not have any creatures? Does spell still work?

Answer 1

If the caster does not have any creatures, that player just doesn't return anything. Each other player is still required to return one creature though.

Since the spell does not have a target (it doesn't use the word target anywhere in it's text), it will do as much as it can when it resolves.

Answer 2

The spell will still work.  Whoever has a creature must return one and those that don't have a creature will not have to return a creature.