Hopefully people have figured this thread is full of spoilers. Easter eggs and other notes.
N1: As noted the room 1 Fallen is from the beholder tower 2 years ago.
At least some of the NPCs for room 2 got to make their own costume for their mage trapped on the dock character.
The Lorigorgon crow's nest was behind the ogre mage right outside room 3. If the ceiling weren't there he could have climbed up and actually been glaring down at you.
The engine in room 4 is the exact same box as the puzzle from a few years ago where you had to plug various tubes into it to get something working. Where you had to feel for the air blowing out. The interior tubes were removed. The walls were from the Drow's Sap puzzle, with the letters removed.
In room 6 I think Rok Montha was using the comfy chair. A lot of his decorations were from the scrael room last year that had the fireplace and wall hangings.
The rainbow bridge is technically not a rainbow. It's clearly YORVBG instead of ROYGB(I)V.
N2:
Presumably the room 1 valkyrie was the same as the N1 room 7 valkyrie.
The room 2 frozen barbarian was often declared by the DM to be the guy that did the naked barbarian run.
The troll drew the figures from the pillar right before that room. You could tell what was coming. I thought it was a frost stone like they have at Coldstone or something. I could have been mistaken on that.
It would have been nice in room 5 if the NPC ever told any of my parties (or specifically me) that we could hide in the cage. Would have saved my newbie group. It would have been a TPK without me.
The DMs seemed to have different names for the giants. The Scottish DM claimed the left one was Damascus and the right was Jeffey. (I think that was what he said.)
The squirrel could be seen in the room 7 tree. He had a little metal helmet and a backpack.
N3: The NPC at the end of N2 that you save from the cage is the same NPC that greets you at the beginning of N3. I think there was a line something like 'Thank you again for freeing me from those giants. Now that I've regained my true form...'
The ghost clues in the days room varied by actor. One actor made a motion for the icon they were by, e.g. plucking out their eye by Odin's face, a number of times corresponding to the number of the week. Another actor showed the same set of motions for the whole week whenever they appeared - swinging both arms wide overhead for the sun, raising a hand up from the waist to overhead for the moon, chopping off a hand to denote Tyr, plucking out an eye to show Odin, and so on.
The correct sword to complete room 5 changed over time.
The dangling pustules in rooms 2 and 6 were pulsating sacs triggered by a UV beam that the NPC (2) or players (6) could trigger. The other sacs were just solid props.
The room 7 boss is named Smoke. Some of the build crew had PTSD reactions upon hearing that.
The weapons in room 7 were the Tesseract (probably a red herring, and the most Eastery Easter Egg in the place), a hammer that sort of was and wasn't Mjolnir, the Tempest wand most likely a reference to the Shakespeare play, the Bigby sceptre likely a reference to the D&D Bigby's hand line of spells, and the orb which had Odin's triskelion (that knot symbol everywhere in the dungeon) but that I never witnessed used.
Viper:
The final big monster is named Wiggles.