How does my XY Archen know fly?

Question

I have a Archen in XY that knows fly that I taught by HM. However, this site says Archen can't learn fly. But I got the fossil legitimately and I don't hack or cheat. So how did this happen?

Comments

Archeops can… maybe it was bred down?

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I don't think it was bred down according to http://pokemondb.net/pokedex/archen/egg , but maybe it was a glitch. Not really sure.

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Are you sure it's an Archen and not an Archeops?

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@Sumwun yes, it was a Archen.
@Astronautical I never evolved it. And I obtained my only Archen by fossil.

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I guess it could also be caused by a previous owner tampering with the game

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It never had a previous owner. And my 3DS is broken.

Answer 1

There is no legitimate way. Most likely a glitch, because I checked and it said nowhere it could learn fly.