Dueling Shows: With The Life and Times of Juniper Lee. Contary to popular belief, this show did not copy off of American Dragon. Both of their respective animation studios finished within a year of each other and neither creator knew of the other's project till they were pretty much on the airwaves. Ironically both shows were subject of Executive Meddling.
Sun Park, the Korean Dragon was supposed to die in "Homecoming".
Also, the episode was originally supposed to be a two-parter.
Honestly, that's just the tip of the iceberg. The series creators had to fight tooth and nail for Jake to be allowed to breathe fire at anything that wasn't a fireplace, or fly around without elbowpads and a helmet. Exactly WHERE in the world is turning into a dragon and flying imitable, anyway?
Originally, the Aztec skulls and Dark Dragon plots were supposed to be based in different seasons, the Aztec Skulls plot taking place in season 2, with the Dark Dragon plot in season 3, likely explaining the fact that the plots weren't given enough time to develop: There wasn't enough time to properly explain all the plot points because they weren't getting another season. Other ideas involved a possibly Darker and Edgier approach with the finale of the second season, involving Sun Park being thrown into a volcano, and also revealing that Jake's Grandma was Chang, both ideas were discarded for being "Too Jetix". Rose was also supposed to stay in New York, but Disney said it was "too confusing" and sent her to Hong Kong. A lot of these ideas would probably have helped the show in the long run.
Fu Dog was originally going to be voiced by Jay Leno.
Haley was originally going to be named Brittany, and was going to be only 5 years old at the start of the series instead of 7. She wasn't even going to have dragon powers either, just Supernatural Sensitivity.
In an earlier draft of the show, Jake was going to be able to shapeshift into the twelve animals of the Chinese Zodiac, not just a dragon.
The whereabouts of Rose's twin would've become a plot point had the show been allowed to go on for another season.
According to one of the writers of the show on the Toonzone forums, at one point there were plans to reveal that Jake's Dad is a werewolf.