A Blooper Nanny is a Blooper with Baby Bloopers found in Super Mario Bros. 3. When she begins to glow, her kids will "explode" away from her making it harder to swim. More kids appear a few seconds later.
Blooper Nannies later appear in New Super Mario Bros. and Super Mario RPG: Legend of the Seven Stars. In Super Mario RPG, only one appeared in the Sunken Ship, and touching it or any of its babies would result in a normal battle with at least one Blooper.