Joseph Chadwick first appeared in the episode "Pet Project", retelling the events of "Be-Knighted" to the Forever Knights. He then shows them an Anterrean Obliterator he had invented in order to travel to the Dragon's homeworld and defeat the entire species.
Unfortunately, its controls are too complicated for humans to handle operating. So instead, Joseph has Sir Morton kidnap Ship in order to use him an Anterrean Obliterator. He also inserts an inhibitor chip that allows him control over Ship turning his green stripes to red. He makes Ship attack Ben's Team when they arrive to rescue him, but Julie manages to appeal to Ship's inner self and frees him from the chip's control.
The ship then betrays and attacks the Forever Knights, causing the entire castle to collapse as he and the team escape. While Sir Morton and his men managed to escape the collapsing building, Joseph Chadwick was caught in the cave-in but was also able to survive.
Joseph Chadwick returns in "Return to Forever" as the new Forever King. He also allied himself with Will Harangue, promising to boost up the reporter's ratings on TV once more in exchange for a hideout in Undertown. There, they began collecting DNA samples of every citizen in Undertown and added it to the Highbreed Pulse Generator, a device the Highbreed used to use to obliterate other species due to their racism (Chadwick lied to Harangue saying the Generator alters DNA and will make the Undertown aliens humans).
After a failed attempt at capturing Jimmy Jones, Chadwick modifies the DNA scanner so that it also scans Omnitrix aliens and revert Ben human. After acquiring most of the Omnitrix DNA, Chadwick has Ben and Rook captured and tied up in their hideout. Jimmy comes to their rescue and, during an essaying battle, knocks Chadwick unconscious with a pipe.
Joseph reappeared in "American Werewolf in London", where he and his men capture Wes Green as well as getting his hands on the last vial of Dr. Jekyll's formula. After drinking the potion, Chadwick grows into a Godzilla-like alien hybrid in order to remove Excalibur from the stone but he fails to do so. He becomes enraged and causes a flooding to occur, prompting the Forever Knights to make a temporary truce with Ben's Team in order to escape the flood. At the end of the episode, the now mutated Joseph Chadwick emerged from the river dragging along the damaged Forever Ninja (who accidentally shot himself with Rook's Proto-Tool due to holding it backward).
Joseph Chadwick was mentioned by Dr. Animo in "Animo Crackers" during the latter's constant bragging over his attempts to take over the world.