Almost sure there will be a reference to:
- The Master
- Children of the Apocalypse
- Vault 13 perhaps
- Boneyard
- The Glow
- B.o.S.
- Mariposa Military Base
- The Hub
- Mentions of Shady Shands as a first step towards forming N.C.R and effects of rule of President Tandi
- Maybe New Reno ....
- Marcus will probably sometimes tell us "how he used to hang out with other dude who later turned out to be a hero of the wastes...and how they mowed like 2.500 Enclave Soldiers...and how Myron was annoying (too bad that he died a year after FO2 tho', because his "comeback" as an older genius scientist would feel quite fitting for area like New Vegas
They'd be remiss is you couldn't ask Marcus about the Master (and him be annoyed about everyone always dredging up ancient history).
(In theory, Marcus should have an opinion of every location he accompanied the Vault Dweller to, and NPC party member)
***If Marcus does not reference Myron they really WILL be remiss, because FO2 had special dialog from Marcus if Myron was in your party, and it can be assumed that Marcus knew that Myron created Jet (a problem that still plagues humanity decades later).