Fringe Connections

Cecil mentions the Observers using a light bomb in "Through the Looking Glass and what Walter Found There", which is what Loyalists threw at Peter in the sewer tunnels in "The Bullet that Saved the World".

Susan Pratt's wardrobe is full of dark colors like Olivia's and Nick Lane's.

A seahorse can be seen hanging from the taxi when Walter listens to music.

The password to retrieve Michael in "Black Blotter", "Black Umbrella", came from the poster for Singin' in the Rain, from which September chose his new name (Donald O'Connor) in "The Boy Must Live".

The Child's happy expression drops when he sees the Observer.

The flower glyph can be seen on the wall in Karen Truss's house.

In "Brave New World (Part 1)" Walter sat in his old cell at St. Claire's from "Pilot".

Michael can show emotion as he cried when he saw Nina's dead body.

The frog glyph can be seen on a door in the pocket universe.

Despite Walternate's efforts to mold Olivia's mind into Fauxlivia's, Olivia kept seeing Peter and Walter in "Amber 31422". Similarly, in "Alone in the World" Peter didn't exist in the rewritten timeline yet Olivia kept having visions of him.

Marshall Bowman had a disk in his hand like John Scott and the woman in 'The Ghost Network'.

A seahorse pattern can be seen in the toxin's molecular structure.

An ambering device, first (nearly) used by the Blueverse Fringe team in "6B", was seen in Walter's storage vault in "The Bullet that Saved the World".

The crane that crashed during the intro has a Massive Dynamic logo on it.

A butterfly can be seen attacking Mark Young.

Ten Observers are present on Liberty island in "The Day We Died" from an assumed total of 12. One of the missing two Observers might be John Mosley, a potential former Observer, who was killed in "The Arrival". See the FAQs for more information (note: FAQs contain spoilers through season 5).

Donald helped Walter set up the pocket universe hiding spot.

A frog can be seen in Walter's Monty Python trip.

Bell was unwell and needed oxygen in Olivia's memories in "Momentum Deferred" which could be because he had lymphoma as Nina revealed in the alternate timeline in "Brave New World (Part 1)".

There is a Massive Dynamic logo on Flight 627's engine.

Butterflies can be seen in Etta's apartment.

The Observers read Nina's phone call from the impressions her sound waves made on the glass in her office in "Anomaly XB-6783746", like Peter did in to hear the phone call Nancy Lewis made in "The Road Not Taken".

Olivia struck James Heath with a candlestick in her dining room, making the title a complete red herring.

The apple glyph can be seen on a door in the pocket universe.