Twenty-One is the only Numberblock in the episode to not be a number from 1-10.
2, 7, and 10 stay vertical in this episode.
Eight only appears as a cube in this episode.
This marks the first time where a Numberblock smaller than Twenty-Seven only appears as a 3D shape (with all coordinates being bigger than 1) in an episode.
On the YouTube upload of the special, meant for people overseas who want to watch it, the thumbnail unintentionally spoils Captain Hexbeard's true identity being Twenty-One.
Despite being a special, people still consider it as the 121st episode of the show.
In reality, Seven rolling across the rotating bridge would NOT keep it balanced.
Details: On every point where Seven's body touches the bridge, a downward force with the same magnitude is applied. However, since the average distance to the rotational axis on both sides aren't always equal, the torque applied on both sides wouldn't always cancel out, and when they don't, the bridge will start to rotate.
Errors
In the subtitles, in the line "You lend us a hand, now it's your turn to take ours", the word "turn" is missing.
Additionally, during the segment where Five helps Three, the subtitles misinterpret the word "yelp" as "yell". This is most likely a mistake as the word "yelp" fits in with the rhyme scheme of "help" and because Eight can be heard saying a "p" sound.
