When Bender is looking at cigars, the cross section of Hacking Jack's suspenders changes from being the same color as the straps to a brighter blue.
This episode marks the second time Fry and Bender have attempted to climb through a steam vent, the first being Love's Labours Lost In Space.
The reason Dr. Zoidberg is blue is because one in every two million lobsters is blue.
Opening theme promotion: BEATS A HARD KICK IN THE FACE
Universes seen: Universe 25 (people-with-no-eyes universe), Universe 1729 (bobblehead universe), Universe 31 (blocky robot universe), Universe XVII (Roman universe), Universe 420 (hippy universe).
Other universe boxes include one that is very cold, one that contains nothing but women, and another one has octopus-like residents. Also, the Benders steal treasure from both a leprechaun universe (gold Bender) and a pirate universe (original Bender).
The two metallic finishes for the Bender type robot are Foghat Gray and Glorious Gold.
Notice that when Fry and Bender jump out of the steam vent, Fry's clothes have shrunk due to the steam.
When Bender and Fry are in the vent, Bender switches his eyes for angled ones. He then looks around the room below, rotating them both in the same direction. However, if he did that, the eyes would have hit and the sound would have gotten Leela's attention.
Edit: She was pretending to fall asleep, so Fry and Bender take the decoy box. She was sitting on the real box.
When Leela is guarding the box at the beginning she is reading a magazine. The cover says its Bigfoot's birthday. This is a reference to the episode Spanish Fry involving Bigfoot.
In an attempt to return to Universe A, the professors created a variety of other boxes. If they all lead to other universes, then the other universes possess a Parabox containing Universe 1. Which still puts Universe 1 in danger, should anyone shake it or destroy it.
Before Leela fell into the box, the walls of the Planet Express building changed from red to blue and back to red. After Leela fell into the box the walls changed back to blue but after the commercial break the walls are red again.
The boxes are shown to contain full universes, but when people jump or look inside, they immediately emerge from the alternate universe's own "parabox" without travelling the enormous distances depicted.
How did the Hippy-Universe Farnsworth manage to build that one Parabox?
In the episode I Dated a Robot (when Fry is doing everything he's ever wanted to do) Farnsworth says there are only two parallel universes - theirs and the one where everyone is a cowboy. However, Farnsworth and his alternate-universe-in-a-box counterpart have now created countless (or at least 1729) parallel universes that didn't actually existed before.
In the scene with everyone sitting around the table (Universe 1 on the left and Universe A on the right) looking at the hologram. Leela 1 is missing her wrist device which is suppose to be on her right wrist but when you see her protesting about being called Universe B the wrist device reappears.
How could the box that fell on Zoidberg A, when he backed into the shelf filled with boxes, fit over him AND the box in his claws) if both boxes were the same size.
When the crew got back to universe A to prevent Hermes from destroying the box, they all jump in the box head first, except Farnsworth who drops the box and goes in feet first. When they arrive in universe A, they all come out head first.
When the crew was picking names for the Universes Leela A suggested Universe A and B, but the alternate Leela said that their Universe would be called Universe 1. Later on Farnsworth A still calls the alternate Professor, Professor B.
Not only is the squishy toy from the "Swedish novelty shop" on Leela's bedside table in the hospital, but on the wall is a landscape picture of a frozen ice planet, similar (the same) to the one in Leela's coma. Hermes also mentions the ice planet.
Opening theme promotion: A BY-PRODUCT OF THE TV INDUSTRY.