what creatures copy themselves

I found the dopplerat which is perfect but its from a 3rd party book.

The only official creature i can find that does anything like this is the black pudding with its split rule.

Are there any official creatures, from any WOTC published material that have a similar ability to copy themselves?

The copies will need to have turns, take actions and be target-able. Really a full creature in itself.

I am specifically not looking for illusions that just cause attacks to miss like the mirror image spell.