Oh My Papa

 is a quest in Fallout: New Vegas.

Quick walkthrough
Speaking to Regis in Red Rock Canyon about allying with the NCR is one way to start this quest. You must convince different members of the Great Khans to speak out against their alliance with Caesar's Legion, in order to convince Papa Khan to ally with the NCR.

Killing Anders in Cottonwood Cove will cause you to fail this quest even if you haven't started it yet.

Detailed Walkthrough
Colonel Moore can be found at Hoover Dam.

Looting Karl's footlocker in the Great Khan Longhouse will give you the note "Karl's Journal." Tell Regis about the journal to convince him to speak against Caesar. Also telling Papa Khan of the journal will complete the optional objective, and the Great Khans will kill Karl.

You need to only convince one of either Jack or Diane to complete their objective. Jack can be convinced via a Speech check. Diane requires evidence that Caesar is hurtful to drug runners. She can be convinced by completing the side-quest Aba Daba Honeymoon.

Melissa is found in the western part of the Quarry Junction area, at a location marked Great Khan Encampment. Simply telling her that women are not allowed to serve in the Legion will convince her to speak against Caesar.

With high enough Speech, you can provoke Karl into revealing his true feelings about the Great Khans. Do this while inside the Great Khan Longhouse, with Papa Khan also present, and the Great Khans will then kill Karl, completing the optional objective.