Ol' Buddy Ol' Pal is an achievement and trophy in Fallout: New Vegas.
Requirements[]
It is awarded for successfully convincing one of the eight Fallout: New Vegas companions (ED-E, Craig Boone, Veronica Santangelo, Lily Bowen, Rex, Arcade Gannon, Raul Tejada, or Cass) to join the Courier.
Bugs[]
This appears to only be triggered by the very first companion you recruit, so if achievements are disabled at that time, recruiting other companions later will not unlock it.