Can they mega evolve?

I assume so, I just haven't designed a Mega or Gigantamax form yet.

I do like the designs and idea, though I kind of wish Gastly would cheer up a little, but I'm assuming they're capable of smiling or showing happiness. They look a bit more eerie than their Ghost/Poison kin. I'm also assuming they can breed with their Ghost/Poison kin.

Anyways, if one were to use this strand of Gastly family, they'd have to keep in mind that A) 4x weak to not only Dark-types but their own Ghost-typing, B) Unless they can learn an immunity negator like "Miracle Eye", they'd probably be in trouble against Dark-types unless they can learn any Bug or Fighting moves.

They definitely can, like other regional variants. And yeah, it's a hefty weakness.

Soooo... I'm assuming they have a way to cover those two Achilles' heels (attack wise). If I were to compare them to another Pokémon family, it'd be Abra in terms of evolution style and intelligence/intellect. Thing is, they'd be a tad more sly than the Abra family, being Ghosts.

Possibly. Not every Pokemon completely covers its weaknesses.

Fair enough. But, you know? "Trade by evolution" has always been a bane to me, esp. if you're playing solo, you ain't got another console, and your budget's a tertiary problem.

A hack called Crystal Clear gets around that problem by using a fellow called the "Tradeback Guy". He does exactly what it says on the box: you give him a Pokémon you need to evolve by trading, you get that Pokémon back exactly the same way you gave it. Because it's counted as a trade, that Pokémon may evolve. You ever met someone like that during your travels?

Fair enough, trading is a pain. I think you can get around it with the GTS? (Putting a mon up and then taking it back)

Right, forgot about that... by the by, what has caused this strand of Gastly to mutate into Psychic-type? Some sorta mystic power in the region they're in, less air pollution than in other regions, etc?

I'm not really sure, honestly.

Very well. They definitely win my vote for "creepy design". I'd probably have them on my team if I needed a swift Psychic that hits hard, but don't have access to the Abra line.

Hehehe :)

Oh, and your Ghost/Psychic Gastly family would put the Ghost/Psychic counter up to 7 if they were canon, and they'd have the honor of being the first non-legendary Pokémon to be such.

Makes me wonder what a Ghost/Fairy Gastly family would be like... I'm thinking pink all over with fairy dust instead of gas, constant friendly smile, perfect for young children, less mischievous and more affectionate.

Maybe, yeah! :3