Question

Can you duplicate moves on a Pokemon without hacking?

Comments

For those of you looking on, the author of this question is banned. I will select an answer to it myself once some time passes.

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Would ingame glitches count as hacking?

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I’m pretty sure Smeargle could do some thinks with this.

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Sketch fails when the user already knows the move it's trying to sketch.

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Actually, my idea was along the lines of glitch Pokemon. An infamous example being Missingno., which starts with Water Gun twice.

Answer 1

There is no legal way to obtain a moveset with two or more copies of the same move, even temporarily. Mimic and Sketch will both fail if they would have that effect, and you can't use TMs, move tutors, or the move reminder to do it either.

If you somehow did have such a moveset, it behaves strangely. You can click either instance of the move, but it will always count as you trying to use the first one. Once the first one runs out of PP, you can continue to click the second, but it will fail with the stated reason "But there was no PP left for the move!" As such, you can never run completely out of PP, and will never use Struggle no matter how long the battle continues.