The Observer can be seen in the crowd after Jones distributes the money with the trackers, walking right to left behind Lincoln.

Agent Lee: I don't know, I've known Murphy since the Academy. He's always been a straight arrow.
Altivia: Oh, I just got kind of a hunch that this other Lincoln is telling us the truth.
Agent Lee: Must be because he has such a trustworthy face.
Altivia: See, I think he's kind of funny-looking.
Agent Lee: You're funny-looking.

Astrid: Walter's just discovered molecular gastronomy.
Walter: I've liquified meat and then placed it in an alginate bath. It's really quite...
Astrid: Quite disgusting.
Walter: That's the thing about scientific inquiry--not every experiment is a success. But I hold high hopes for the Parmesan ice cream.

Lincoln: I need to be a part of this investigation. I lost a partner.
Peter: I lost a universe!
Lincoln: You're scared.
Peter: Yes, I am scared. I'm scared that every day I stay here, the people that I love get farther and farther away from me.

Farnsworth: Are you really from another timeline?
Peter: Yeah, I think so.
Farnsworth: Cool.

Elizabeth Bishop: I saw how much you loved him. Your strength...
Walter: Not strength! Hubris. And I've been punished for it ever since.
Elizabeth Bishop: By whom?
Walter: By God. By a deity, whatever you want to call it. And I understand, I deserve it. No man should do what I did.
Elizabeth Bishop: You made a mistake. That's what being a man is.
Walter: It was more than a mistake. I broke universes. I asked for a sign of forgiveness, but I got nothing. There is no absolution for me.
Elizabeth Bishop: Well, I don't believe that. I forgive you, Walter. I forgave you a long time ago. And if I can, God can.

Walter: I lost the people I loved most and I imagine you miss them too, the people you've left behind.
Peter: Yes I do.
Walter: I will help you, Peter. I--I will help you get home. The last 25 years, I've spent thinking about losing my son. I thought I was an expert on loss. Maybe that's why you are here, because there are still things that I need to learn. What?
Peter: I just spent the last several days with the other Walter, and I was very surprised to learn he was not the man that I thought he was. But I am not at all surprised to learn that you are.
Walter: Is that a good thing?
Peter: Yes, Walter. That is a very good thing.

The glyph/code spells out DEATH.

On the Other Side, they appear to use either Franklin or Teddy Roosevelt's face on the $100 bill, rather than Benjamin Franklin.