We have a quick question that needs an answer.

If you replace Ventry with Void, then later replace Void with Sentry, if Sentry is KO'd does Ventry come back?

EMERGENT EVIL: Sentry and Void can use Multiattack ability. Give Sentry and Void a power action if it has no tokens and replace it with CW #035 Sentry or CW #045 Void on the same click number. When the replacement character would be KO'd, you may instead return this character to the map on click #10.

We?They are still the replacement and therefore still eligible for the power.

He is part of the collective. Resistance is futile.

Added irrelevant detail only because it's a funny situation.
Although not actually uncommon, given Beast Boy, Hank Pym, and Punisher all have multiple replacements.

No one knows, so ask your judge before you try it in a big game. My guess is yes, because it's still the replacement character.

Actually, we do know: that will work according to the rules. That doesn't mean your particular judge will recognize that and rule it that way, so it's still a good idea to ask.