How do Invisibility and Mirror Image stack?

Question

My character finds himself in a situation where he has access to both the mirror image spell and has the ability to become invisible.

Ignoring the means by which he becomes invisible (he's not doing anything that'd end his invisibility) what happens when these two effects stack?

Mirror Image

• Three illusory duplicates of yourself appear in your space. Until the spell ends, the duplicates move with you and mimic your Actions, shifting position so it's impossible to track which image is real. You can use your action to dismiss the illusory duplicates.

• Each time a creature Targets you with an Attack during the spell's Duration, roll a d20 to determine whether the Attack instead Targets one of your duplicates.

Invisible Condition

• An invisible creature is impossible to see without the aid of magic or a Special sense. For the purpose of Hiding, the creature is heavily obscured. The creature’s location can be detected by any noise it makes or any tracks it leaves.
• Attack rolls against the creature have disadvantage, and the creature’s Attack rolls have advantage.

So, are the mirror images also Invisible (Disadvantage to attack them) - which seems... odd. Although I guess you could argue the mirror images also mirror whatever sounds and other perceptual clues your actual form is making, even if they aren't obviously visible.

Or are the mirror images visible but you are not? No disadvantage if someone happens to attack a duplicate, but they will have a disadvantage if they attack you.

Or spell fails completely, because of reasons?

Answer 1

The images also become invisible; hence they become useless until the invisibility ends.

Mirror Image tracks how you appear. So, for the same reason, and in the same way that it stacks with blur, it also does stack with invisibility, meaning that the images also become invisible. And invisible mirror images can no longer distract an opponent, so they become completely useless. (Note that mirror images are only effective as a sort of visual illusion, as discussed in this rpg.se question.)

Unofficially, Jeremy Crawford answered this question on twitter (May 24, 2018):

Mirror image creates illusory duplicates of you that imitate your appearance. If your appearance goes away—you become invisible, for example—then the duplicates imitate that too. An attacker isn't affected by mirror image if it can't see the images.