They keep in contact with Sovereign and mess around on the journey. They also make fun of others.
Sov: OHGODTHESHIPSNOTTHESHIPSAHHTHEIRINMYCITADELAHHNOTTHESHEPARDAHH!
Reaper: huh. Sovereign failed.
Reaper2: Fine. Lets walk.
(Later)
Reaper 1: Someone should kill that Shepard guy.
Reaper 2: It's just some sort of rumor
Reaper 1: You sure?
Reaper 2: Sovereign sucked anyway. I don't think one human could take one of us though...
Harbinger: I'll take him out, even make him head of the Human reaper? Allright?
Reapers 1&2: Sure.
(Later)
Reaper1: Oh Harby, your back. got worried there.
Harby: He took out the Collecters.
Reaper 2: That Shepard dude survived a colony attack? Oh man
Harby: No, he killed all of them. And the Human reaper.
Reaper1: You should relay that information to the Evil Council of Reapers.
ECoR: We have reached an agreement. This Shepard does not exist. Harbinger had a 43.65% chance to malfunction at this range.
Harby: ... You're just going to ignore this threat? Shepard is REAL! We have to stop him!
ECoR: We will see soon enough. The Alpha relay is only a few million seconds away.
At the Alpha Relay:
ECoR: See?
(Relay blows up)
ECoR: Just a malfunction. We will fly manually towards the nearest system.
Harby: It was Shepard! You can't deny it any longer!
ECoR: Ah yes, Shepard. The alleged human who destroyed two of us and halted 3 of our plans. We have dismissed this claim.