Fringe Connections

The creatures from "Snakehead" were used as a weapon against the Observers and Loyalists in "An Enemy of Fate".

This episode reveals that there is more than one Observer. The intro sequence since the pilot episode has had a single frame that says "OBSERVERS ARE HERE".

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

In "Black Blotter" Walter had a vision of his scuffle with Nina at Reiden Lake from "Peter" and later recalled other memories from that day.

Carr's work review sent to Astrid from his previous employer shows that in the three years prior to his dismissal, he only missed three days of work. He was out for only one day each year and each year it was the same day: Valentine's Day.

Butterflies can be seen in Olivia's bedroom.

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".

Madison Square Garden in the Redverse is quarantined in amber.

A hand can be seen outside the entrance to the daycare center.

September's security system flashed the 'green-green-green-red' pattern from "The Equation" before exploding in "The Boy Must Live".

Walter's pose as he listens to the Mozart Requiem is a reference to the iconic Maxell tape advertisement from the '80s.

A frog can be seen on the dock when Walter is high.

There was a white tulip in Walternate's bedroom in "Immortality" when he was struggling with what he had to do to save his world, suggesting that the symbol has meaning for him just like it did for Walter in "White Tulip".

One of the envelopes Peter sorted through said "Thank you for your support!", a direct message from the creators of Fringe to all the fans.

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

Olivia noticed the book "Burlap Bear Goes To The Woods" in Max's room in "The Abducted". This is the same book Rachel read to Ella in "Unleashed".

When Nina looks in Bell's storage room for his copy of the First People book the camera pans by a copy of 'Dr. Spock's Baby and Childcare'.

A butterfly can be seen painted on the side of a white trash can.

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)".

The green and yellow posters in the diner represent how this new timeline with the yellow/amber title sequence is starting to merge with the original timeline with the blue title sequence now that Peter has returned (blue + yellow = green).

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

In "Grey Matters" Walter's brain pieces were stored the heads of living people. In "Letters of Transit", in the altered timeline, they were stored in Massive Dynamic.

Jones said there are 10 tests for Olivia in total. The first was a box of lights that Olivia had to turn off with her mind.

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