Is Mewtwo and Yu-Gi-Oh voiced by the same person?

No, Mewtwo and Yu-Gi-Oh! are not voiced by the same person.

* Mewtwo is voiced by Dan Green in the English dub of the Pokémon anime series.

* Yu-Gi-Oh! (specifically, the character Yugi Mutou) is voiced by Eric Stuart in the English dub of the Yu-Gi-Oh! anime series.

While both Dan Green and Eric Stuart are popular voice actors in the anime industry, they have distinct voices and are not the same person.