Dr. Julien, also known as the Tinkerer, was an inventor who created several impressive robots, including Echo Zane, the Falcon, the Juggernaut, Tai-D, and most notably, his son Zane, who is also the Elemental Master of Ice and the first Nindroid. Julien took care of Zane in the years following his creation, before erasing his memory (to prevent Zane's memory of him passing away) shortly before passing away. However, Samukai resurrected Julien, using him to build vehicles for the Skulkin army. For much of his restored life, Julien was imprisoned inside a lonely lighthouse, which was guarded by a colossal sea creature - the Leviathan.
Shortly before the Final Battle, the ninja journeyed to the lighthouse prison, where Zane reunited with his father. With the ninja's help, Julien escaped the lighthouse due to Zane freeing the Leviathan, allowing it to escape as well. Julien would go on to create several vehicles for the ninja, including the Earth Driller and Fire Mech, all while bonding with his son. Unfortunately, Julien had trouble keeping up with the ninja and stayed behind when they went to the edge of the Dark Island to combat the Overlord. Aspiring to make himself useful, Julien flew the Bounty to the scene of the battle, using the ship to block a missile that would've harmed Lloyd, Wu, and Misako. After leaving the Dark Island and returning to Ninjago City, Julien witnessed the Ultimate Battle between Lloyd and the Overlord, and after Lloyd won, Julien rejoiced with everyone else.
Following the final battle, Dr. Julien passed away again. At the end of the conflict between the ninja and the Nindroids, Zane sacrificed himself to defeat the Overlord, with his original body being destroyed in the process. At one point in time, a statue of Julien was erected in Birchwood Forest by Zane. On the Day of the Departed, Zane commemorated Julien at his statue. Meanwhile, Cole accidentally revived the ninja's old enemies, including the corrupt Nindroid Cryptor, who attacked Zane and destroyed Julien's statue. Once more, Zane defeated Cryptor, preserving his father's image as a trailblazing inventor.
