Koffing and Weezing are not obtainable in Pokémon X and Y so you'll have to wait for the release of Pokémon Bank and Poké Transporter on December 27th of 2013 to transfer one from any Generation V games (Pokémon Black, White, Black 2 and White 2).
Alternatively, you can ask a friend to trade you one or look for one in the GTS after this date.
Weezing does not evolve in Pokemon Ruby.
Yes You Can Get A Pikachu In Pokemon X and Y.
Weezing is #110 in the national pokedex, and it is a Poison type Pokemon.
The Legendary Pokemon available in Pokemon X/Y are:Xerneas (X only)Yveltal (Y only)ArticunoZapdosMoltresMewtwoZygarde
Weezing can be found in Route 227 and Stark Mountain on Pokemon Pearl. Weezing isn't rare in the two locations it appears in.
Pokemon X and Y are sold at MSRP of $39.99 (CAD)
718
Prof. Sycamore will give you the oval charm in Pokemon X and Y.
Pokemon capable of learning Psywave as an Egg Move in Pokemon X and Y are Latios (Pokemon) and Gastly (Pokemon).
Koga's Pokemon are: Koffing Muk Koffing Weezing
I believe X is stronger, but Y looks cooler.
*Mew is not catchable in Pokemon x and y, but you can get him online from wondertrades and such. Mewtwo however, is catchable and you can find him in the cave in pokemon village.