And if the mother doesn't have the hidden ability, the baby never will, even if the father has it. If the mother has a regular ability, the baby has an 80% chance of having that ability and 20% of having the other ability (if there are two). If there's only one normal ability, of course it will always have that.
If you breed with Ditto and the Pokemon normally has two normal abilities, the chance will be 50% of either, no matter the mom's ability.
Just wake me up when Tokimeki Memorial 4 is announced. g Rod "hing RodCopper Fishin For fishing.