The huge drone that Preston Stormer fights in the flashback scenes was actually designed by a fan for Official Bionicle Building Contest #53, which was held on the LEGO fansite BZPower.com. It was revealed early on that the winner model will have a special purpose, but this was kept secret until the cartoon aired.
Several characters that appear in the cartoon are not based on existing LEGO models. Professor Zib and his floating helper Quadal are prominent characters despite not having toys to promote. Sir Makuro, the giant evil drone, the female reporter, and a bunch of other side characters also belong to this group.
The name of Makuhero City comes from a play on the expression "make you a hero". This is fitting, considering the city's primary facility is the Hero Factory. It also references its founder, Akiyama Makuro.
Although the earlier episodes had a basic continuous story, later episodes threw out the continuity almost entirely, and instead told stand-alone stories, all of which ended in unresolved cliffhangers. The final episode in particular utilized a different design style and replaced all of the voice actors. Some believe this was because LEGO had already decided to cancel the series eventually as early as 2012, and most of their attention was diverted to preparing the relaunch of their more popular BIONICLE toy-line.
A theatrical live-action movie adaptation by Universal Pictures was considered to go into production in 2012, to be written by Michael Finch and Alex Litvak. No further news came of it since, and with the cancellation of the Hero Factory toy line and cartoon series, the movie was also canceled. It is unknown if the project ever moved beyond its planning phase.
According to a blog post written by one of the series' concept creators, Hero Factory was initially envisioned as an entrance to a wide and expansive universe, and its purpose was to satirize superhero stories. There was to be a dark secret behind Hero Factory, which would have been revealed gradually, eventually turning the series on its head. The supposed lesson was that heroes aren't simply built or manufactured, but they become heroes by achieving great deeds. The series' tone was to be based on The Incredibles (2004). This proposal was completely dropped by the LEGO Company, and the Hero Factory series was released as a simplified and heavily sanitized "good vs evil" story, exactly the thing its creators have set out to criticize. However, fearing that the blog post was worded too emotionally and could easily be misconstrued, the post was later redacted.
The female reporter robot Daniella Capricorn wasn't based on an official Lego model. Her upper body was made up by the designers, but her legs were actually modeled on "erotic" female Bionicle models made by fans that can be seen on certain parts of the internet. They used the exact same configuration, meaning that the designers of the show looked up unofficial online Lego porn to get inspiration for the cartoon's side characters.
The series' original concept poster featured a red Hero, possibly a prototype for William Furno, posing in a generic superhero stance with a huge grin, while unbeknownst to him a small robot dog urinates on his foot, taking away all his credibility as a hero. The comical tagline was "Prepared for (Almost) Anything". These satirical elements were removed when Lego picked up the concept.