you cant
I am sorry but there is no offline co-op
Go to on line as usual, and go to your challenges and pick undead overrun.
yes, you can have up to 4 players offline
its on Undead Nightmare
You can't play coop on Red Dead Redemption or Undead Nightmare.
You cannot get Red Dead Redemption - Undead Nightmare on the PlayStation Portable.
No, if you buy the one for 20 dollars that is undead nightmare but not the original. The only way to get both is buy the Original Red Dead Redemption and then buy the Undead Nightmare add-on
No you cannot join with the zombies in undead nightmare
Well, you can get Undead Nightmare into the Red Dead Redemption disc if you download it from the PlayStation Store.
I would say Undead Nightmare is a DLC because you die in The 1st Red Dead Redemption...
You have to get in a fight with them.