While a face-up "Mokey Mokey" is on your side of the field, if a Fairy-Type monster on your side of the field is destroyed, the ATK of each "Mokey Mokey" on your side of the field becomes 3000 until the end of this turn.
Rulings
Individual Card FAQs
If the effect of "Mokey Mokey Smackdown" is activated (by a Fairy-Type monster on your side of the field being destroyed), and afterwards you Summon a "Mokey Mokey", that "Mokey Mokey" will also have 3000 ATK even though it wasn't on the field when the Fairy-Type monster is destroyed.
Spell|
Continuous