Why does my newly bred Froakie know Hydro Pump, when Hydro Pump is not one of it's egg moves?

Question

Was breeding Froakie with it's hidden ability and proper nature (doing the proper breeding process and stuff), and every single one that hatched had Hydro Pump here. Was thoroughly pleased about this until I looked here and found out, "Wait! Hydro Pump isn't one of it's egg moves for Pokemon X and Y!
I'm scared, because I did this all legit, but for some reason, it knows a powerful water type move it should not know at all, despite this Greninja being from the Friend Safari (and the Ditto being caught outside the cave where Mewtwo is). Can someone explain what happened during breeding? Yes, my Greninja does know Hydro Pump.

Comments

Are you sure the parents were Greninja and Ditto?

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100%, because when I had 2 at first, I wasn’t getting the hidden ability. I was getting Hydro Pump, but no hidden ability, and I was focused on the hidden ability, so I switched to Ditto, which I knew let me guarantee that I would pass down the hidden ability, but for some reason it still passed down Hydro Pump, even though both parents need to know the move... well anyways, I still got my Protean Froakie for my re-play of Pokémon Y (was bored), so I’m not too worried anymore.

Answer 1

It is because if the parent knows a move the child can learn through level up. Froakie learns Hydro Pump at level 48, so if the parent has it, any hatched Froakie will also have Hydro Pump

Comments

Are you sure? Bulbapedia says level up moves pass down only if both parents know it.

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But I think because the second parent was a ditto, it mirrors the moves greaninja has