Gengar ex features a distinct 3D art style, while the border in this card is silver as it was for ultra-rare and secret-rares during the set, and the card itself displays a fitting purple mist background which serves to support the unique art style.

Source: https://screenrant.com/pokemon-tcg-most-expensive-gengar-cards-worth-money/

Gengar finds out the truth of its abandonment in the episode and lashes out at its former trainer in a fit of rage.

Source: https://www.cbr.com/pokemon-anime-saddest-backstories/

So, learn your Pokemon's skills and build an army of those who fight well, like Gengar, Blissey, Vaporeon.

Source: https://www.pocket-lint.com/games/news/138270-best-pokemon-go-tips/

While Mr. Mime may have had good intentions, now that Gengar has been added to the mix, any and all ambiguity has gone out the window.

Source: https://gamerant.com/best-coolest-pokemon-fusions-wish-were-real/