Mewtwo: No More Armor

What's a background?

So I was watching the first Pokemon movie yesterday and I was like: MUST. DRAW. SUPER. COOL. MEWTWO. >.<

While I was watching, I had some thoughts....
*gangsta-fied re-enactment*
DA-YUM! SOMEBUDDY'S GOTTA USE A DARK TYPE POKEMON ON DAT BE-YOTCH!!!
(realizes there are no Dark type pokemon in the Kanto Region)
DAAA FUUUUUU--!?
*end gangsta-fied re-enactment*
So yeah, dark type pokemon are immune to psychic type attacks, so it wouldn't affect them, right?

Problems:

No dark type pokemon in Kanto, only dark type moves (i.e. bite, crunch)
Pikachu can defeat Golem/Onix/other ground type pokemon with ELECTRIC type moves?
I'm such a nuuuuuuuuurd :3