Since Mortal Kombat 9 was released, there seems to have been quite a bit of confusion as far as how to access the Klassic Costumes. Various people thought they were hidden somehwere in the Krypt, or by beating the hidden kombatants.
Originally they were only available via DLC code depending on where you preordered the game from.
Now, they have finally been released on DLC so anyone can purchase them. The pack is called Klassic Skins Pack #1 (which means there will be more on the way in the future).
The Klassic Costumes that are currently available: Sub-Zero, Scorpion, Reptile, Mileena, Kitana, Ermac, and Jade.
Sub-Zero, Scorpion, and Reptile’s Klassic Costumes also come with their Klassic Fatalities, but the rest do not.
On Xbox Live the pack costs 400 points, or $4.99 on PSN.
Battlefield Hardline General Tips & Tricks Guide
Grand Theft Auto V – Triathlon / Races / Running / Sports Guide
Metal Gear Solid V: Ground Zeroes – Easter Eggs and Secrets
Grand Theft Auto V: Aerial Challenges Guide – Knife Flight Guide
Call of Duty – Black Ops 2: How to Get Gold Guns