Trivia: The periodic chart on Walter's wall contains the elements Osmium and Lutetium. This is a clue toward the next episode, "Os."
When Walter enters his Jacksonville office, at 9"40, the periodic table of elements is visible behind him, and there seem to be 117 elements on it - but elements 110 through 117 were not discovered until 2004-2009, though the scene takes place in 1985.
Alternate Earth general differences:
- The Dodgers are still in Brooklyn, having never moved to Los Angeles.
- Airplanes were never invented or are not in common use (note Peter's fascination with them).
- There are no peanut M&Ms.
- Americans use 24-hour military time and not 12-hour AM/PM time.
-The space program is based out of Jacksonville, Florida, not Cape Canaveral.
In the scene where Elizabeth talks to young Peter in the kitchen for the second time, as she says "Listen to me," you can see the shadow of the boom microphone moving on the black kitchen counter top next to the pile of towels.
Trivia: The Observer can be seen inside Bishop Dynamic as Walternate passes by him in the main entrance lobby.
Trivia: The glyph code for this episode is SWITCH.
Elizabeth: He is in such distress. He-he looks at me, and he doesn't trust me. I'm his mother, but no matter what I say, he...
Walter: Elizabeth, Elizabeth, you are not his mother. He's a little boy very much like our son... and we saved his life.
Elizabeth: No, you...you-you saved his life. I'm just trying to keep him alive.
Elizabeth: You know, tulips don't usually grow in areas like this.
Young Peter: Well, then what are they doing here?
Elizabeth: A professor who was working here missed them, so he imagined a tulip that would grow in this climate and he invented them. He used his brain and his imagination to turn the world into what he wanted it to be. How would you change the world if you could, Peter? What would you wish for?
Young Peter: I wouldn't make stupid flowers grow.
Elizabeth: What would you do?
Young Peter: I'd go home.
Walter: Don't you see what I've done? I crept over in the night, and I stole their child. If we don't return him, they'll figure it out, and they'll come after him, after us. I know because that's what I would do.
Elizabeth: So you would sacrifice one for the other... this little girl Olivia for Peter?
Walter: No. But for thousands of others, or millions... it would have to be considered.
Elizabeth: You know what? Maybe it was plastic surgery. Or an alien able to take on any shape he wanted. We've considered all your theories, Walter, and none of them have brought our son back. It happened. It just happened, and it's inexplicable.
Walter: Nothing is inexplicable, Elizabeth. Science seems like magic to primitives. Something happened in this house and we have to go over it, and over it, until we find out what we're missing!
Elizabeth: Listen to me. Sometimes the world we have is not the world we want. But we have our hearts and our imaginations to make the best of it. I will promise you this. I will be the best mother I possibly can be to you. I'll take care of you, I'll protect you, and I'll never let anyone take you away from me. No one. Not ever.
Anna Torv, Joshua Jackson, Lance Reddick, Blair Brown, and Jasika Nicole are credited but don't appear.
Injoke: The tower puzzle that Olivia attempts to solve is the same one used to test a young Sydney Bristow in the J.J. Abrams' produced Alias, in the episode "The Indicator".
The opening credits are done in the same retro style as the season 2 episode "Peter."
Canada: February 25, 2011 on Citytv
Australia: March 2, 2011 on GO!
Latin America: April 5, 2011 on Warner Channel
UK: April 27, 2011 on Sky1
Sweden: July 22, 2011 on Kanal 5
Finland: December 14, 2011 on MTV3
Poland: May 7, 2012 on TVN
Czech Republic: April 8, 2013 on FANDA