Here are some recurring "Easter egg" screen shots from the Fringe episode "Os":






Next Episode Clue: The Fringe episode "Subject 13" contained two posters of the periodic table of elements, the standard Mendeleev model, and the much newer Circular model (we won't mention the fact that both versions are too modern for 1985...). In either poster, you can see the symbol for Osmium - "Os", the titular element of the episode:

KRICK: I work in aeronautics. A few months ago, I was contracted to develop a new alloy for military aircraft-- A metal dense enough to keep pilots safe from ground fire, but still allow for flight. I wasn't having much success. And then I combined two elements. Rare elements.
WALTER: Osmium and lutetium.
KRICK: And that's when it happened. I'd combined two of the densest elements on earth, and somehow the result was a new molecule... A molecule lighter than air.

 Violet Sedan Chair: Walter has a Violet Sedan Chair sticker on his make-shift bong.

Some other interesting screenshots from Subject 13:


Soul Magnets: Walter discovered some interesting research in William Bell's old files:

WALTER: He posits here that a person's soul or consciousness continues to live on after death. And all it needs is a vessel or a host to return to. 

NINA: Yes, I remember. It was one of William's more extreme flights of fancy.

WALTER: All he'd need to do was to prepare someone by inserting a microscopic soul magnet inside them. And he proposes using injections, food, or a cup of tea--

NINA: Walter--

WALTER: What if he did it? What if he's done it? What if he's done it, Nina? What if he's done it? Then all we have to do is to figure out how to trigger the magnets to summon the soul back into the host, and he'll be back here with us.

In the episode "Momentum Deferred", when Olivia recalls her meeting with William Bell, we can see that he serves her a cup of tea. Presumably, filled with soul magnets. Here is a video of that scene:


(Click the image above to watch the video directly in the FringeTelevision YouTube channel.)