Why Can't We Be Friends?

Why Can't We Be Friends? is a side quest in Fallout: New Vegas.

Quick walkthrough
Enter the tunnel to The Sulfur Caves under Vault 19 and choose one of these options:
 * Kill all the fire geckos for Samuel Cooke to help the Powder gangers create bigger explosives and join with the Great Khans.
 * Help Philip Lem seal access to the cave surrendering the escaped convicts to NCR or joining the Great Khans (Speech 60 required).
 * Blow up the mines and Vault 19 killing everyone inside.

Detailed walkthrough
Talk to Samuel Cooke and Philip Lem in the Overseer's Offices located right next to each other and getting the two quest options; then go to the living quarters of Vault 19. There are a few frag mines and fire geckos you have to worry about once you enter. From the living quarters find the common room with the pool tables and a hole in the floor. It will bring you down to the Sulfur Mines. Now you may either choose to kill all of the fire geckos for Samuel Cooke, seal the caves for Philip Lem, or blow up both the caves and Vault 19.

Samuel Cooke
After you have killed all the Fire Geckos go back to Samuel Cooke and you will get some Powder Ganger fame and 300 caps. He then sends you to the Red Rock Canyon to meet with the the Great Khans; where you have to convince Papa Khan to join forces with the Powder Gangers in the vault. After you have convinced Papa Khan, return to Samuel Cooke to finish the quest.

Philip Lem
In the caves, find the Microcline Rock and activate it. You will need a Science of 40 or more to receive the options. Choose to "Plant enough C4 to blow up the caves" (Explosives skill of 60 and 3 C-4 plastic explosives). Return to Philip Lem and let him surrender the gang to NCR to finish the quest, or with a Speech of 40 you can convince Philip Lem to join the Great Khans. Speech check is not required if you are liked among the Great Khans. He requests that you act as a liaison, requiring you to visit Red Rock Canyon and talk to Papa Khan to secure their alliance. Return to Philip Lem after talking to Papa Khan to finish the quest.

Blow up Vault 19
In the caves, find the Microcline Rock and activate it. Choose to "Plant enough C4 to destroy the caves and the vault and get out of the vault as soon as possible" (Explosives skill of 50 and 5 C-4 plastic explosives).
 * WARNING: This will fail the quest, and you will not earn any XP. You will be transported to the outside of Vault 19 and the Quest Failed message will pop up.

Journal entries
For Philip Lem:

For Samuel Cooke:

Bugs

 * If following the Lem quest line, the map marker will tell you to go to the "Sulfur Caves" entrance (now blown up and billowing smoke) to find and talk to Lem about joining the Great Khans after talking to Papa Khan. Lem is actually located in the Overseer's Office, and if you've opened the stairs leading to the sulfur caves he can sometimes be found stuck there.
 * If you enter the Overseer's Office from the elevator entrance (Hard Lock) in Sulfur Cave and open the Overseer's Office with the Average Terminal, or just go through this route at any time, you may have some issues with your companions as mentioned above in less detail. When you ascend the stairs into the office your companions become confused and instead of following you up will run out the door back into the caves. If you are at the top of the stairs with a companion and run down they will run back into the vault. It is possible, however to keep your companions with you during this if you manually "push" your companion up and down the stairs. Just crouch and slowly move them and they will glide up, or down the stairs from your push.
 * This seems more like a path finding issue. Your companions will go back the way you came and reappear by your side a few minutes later, the same way they will if you jump from a ledge, (yes, it's an oddity).
 * If the player chooses to destroy the sulfur caves and the vault, but didn't kill Cooke personally, then the ending sequence will still show Cooke still alive and the Powder Gangers terrorizing the Mojave.
 * After speaking to Papa Khan for Cooke and returning with the news, it is possible to enter Lem's office through the main door (not the overseer tunnel) to see the piles of bloody entrails. Returning to Cooke will not trigger the dialogue where Cooke admits to killing Lem; he asks you once again to go and speak to Papa Khan on their behalf even though this is now impossible.
 * It is possible to re-enter Vault 19 on the PC version using the no-clipping command to pass through the mound of earth that appears over the entrance. (Not a bug, noclip is cheat.)

Behind the scenes
"Why Can't We Be Friends" is a reference to the song recorded by WAR in 1974.

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