Jackie Chan absorbing the beast-like Earth Demon chi in Season 5 may be seen as a reference to the real Chan being the Chinese voice of another, friendlier beast from 1991, who was voiced by Robby Benson in America. In addition, Chan was also the Chinese singing voice of the Beast, and was the Chinese counterpart to Peabo Bryson in singing the title theme.
Dueling Works: The second and third seasons of JCA were aired alongside The Mummy: The Animated Series. JCA managed to get a few more seasons in than The Mummy, which was put in stasis for 5 years after two seasons.
Keep Circulating the Tapes: The only official DVD releases this series got were 3 single disc sets containing 3 episodes each, which don't even comprise the whole of Season 1, though a Season 1 set has been made but good luck finding it. A Season 2 DVD set was released in 2012, but it's out of print and a bit pricey. The first two seasons can be found on Hulu. Fortunately, the entire series can be purchased off of iTunes and Amazon Instant Video.
When Hak Foo originally debuted in the first season episode "The Dog & Piggy Show", he was voiced by Jim Cummings. After he became a regular, starting with season 2, John DiMaggio took over the role. In "Deja Vu", when Jackie relives the events of Hak's debut episode DiMaggio still voices the character.
Likewise, Julian Sands voiced Valmont, but only for seasons 1 & 2. Greg Ellis voiced him in season 3 and Andrew Abselon voiced his handful of appearances in season 4.
After originally being voiced by Corey Burton, all other appearances by Xiao Fung have him voiced by Glenn Shadix, who also voiced Tso Lan (Burton was actually never credited as Xiao Fung in any of the episodes where that character appears).
They even lampshade it. Season 1 had the team looking for the 12 Talismans of Shendu, and Season 2 had them trying to prevent the unsealing of the 8 Demon Sorcerers. Season 3 had the Talismans destroyed, and their powers transfer to their animal namesake (the same magic in a new container), and Season 5 had them looking for the artifacts of the Immortals who imprisoned the Demon Sorcerers (same elemental powers in new containers). Season 4 is the only completely original season with the Oni Masks.
The entire main story arcs of all five seasons follow the same basic structure: Locate and obtain potentially dangerous (if not apocalyptic) magical powers scattered all around the world, before the bad guys get to them first.
In "Black and White and Chi All Over", the scene where Drago is trying to recruit new henchmen (with mostly pathetic results) plays out a lot like a gag from "Tough Luck" when Finn was trying to start his own gang.
Schedule Slip: JCA managed to become a small part of September 11th in a few ways, which affected the demon portal arc with the rest of Shendu's family and one of the real Chan's planned films.
The airing of the JCA Season 2 premiere "The Stronger Evil" (along with the rest of the Kids' WB! lineup for Fall 2001, which included the American debut of Yu-Gi-Oh!) were postponed by two weeks due to the 9/11 terrorist attacks from Al-Qaeda, which started The War on Terror. This was probably due to a trend of censoring and editing out any images of the now-destroyed World Trade Center; for example the next Season 2 episode "The J-Team", which included a brief shot of the NYC skyline. One of the extra episodes that took place during Season 1, "Through the Rabbit Hole" (the final episode in the Season 2 docket), had already aired the Saturday before the attacks, and the other two Season 1 fillers aired in the two weeks where "The Stronger Evil" and "The J-Team" were supposed to air, followed by a Monday episode which debuted Tohru's mother (and the first episode on the production order that follows the "Demon World" episodes), then the season officially began at the end of the month.
On a related note, the real Jackie Chan was supposed to star in Nosebleed, a movie about a window washer working at the World Trade Center who foils a terrorist plot, which was immediately cancelled for obvious reasons. Allegedly according to an urban legend, Chan even missed out on attending the planned filming that was supposed to begin on the morning of September 11, 2001.