Plumbers

The Plumbers are an intergalactic law-enforcement organization that makes use of many high-tech gadgets and weapons to protect the planets in the universe from various alien threats and attacks.

History
In the original series, the Plumbers are a secret government organization that protects the general public from any alien threat. Their main adversary was the alien warlord, Vilgax. Max Tennyson was a member of the Plumbers in his youth and was ultimately the one who defeated Vilgax. Most of the Plumbers eventually disbanded; however, a few of its members (like Max and his relatives) remain in a semi-active capacity.

Max is effectively forced out of retirement after his grandson, Ben Tennyson obtains the Omnitrix. Max uses his experience as a Plumber (along with various Plumber gear and weapons) to aid Ben in various battles along the road.

In Big Fat Alien Wedding, it is revealed that the Plumbers have had a generations-long feud with the Lenopans. However, when a close relationship was formed between Plumber Joel Tennyson (Max Tennyson's nephew) and a Lenopan named Camille, a truce was forged as a result of their relationship and their wedding was to be the first ever marriage between a Lenopan and a human and was meant to put an end to years of fighting. Camille's parents and ex-boyfriend tried to stop the wedding; however, they were defeated by the combined efforts of Camille and the Tennysons and thus, the two were married. Though Joel's parents were against the marriage at first, they later realize how unfairly they had treated Camille and finally accepted her as their daughter-in-law, thus putting an end to the feud.

The Plumbers' main base is located inside of Mt. Rushmore, where the Null Void projector and the Sub-Energy are stored. In the episode of Truth, the Null Void projector was stolen by Phil Billings as a part of scam to profit from catching aliens he himself had released; however, his plan was thwarted by Max and Ben. There is also a base located within Fort Knox and the Seattle Space Needle and a map detailing the location of all the plumber's bases in USA revealing there is at least one per state. Max stated that there is one base built into every major military base in the country. In Alien Force, the Plumbers are revealed to be an inter-planetary law enforcement force, with both human and alien members.

However, Max discovers that the Highbreed and their minions, the DNAliens, are up to no good and he warns Magister Labrid there is trouble brewing on Earth. Labrid quickly discovers Max has gone missing and mistakenly tries to capture Ben and Gwen, believing that they were stealing the Omnitrix. Upon discovering who they are, he asks for their assistance in discovering the reason for Max's disappearance. The three of them manage to interrupt an arms deal between the Forever Knights and the DNAliens, with Ben's old-rival, Kevin as the middle-man. After a brief battle, they captured Kevin and convinced him to help them find out what was going on, Kevin decided to help as he had not been paid. They tracked the weapons back to one of the Forever Knights castles. During a battle with the Forever Knights, Labrid is fatally wounded. His dying wish was for them to finish their mission and charged them with protecting the Earth from this new threat.

In Everybody Talks About the Weather, it is revealed that Plumbers possess special badges. All Plumber Badges bear the intergalactic peace symbol. There is also a practice where alien Plumbers who have inter-bred with humans give their hybrid-offspring a Plumber Badge to prevent them from being wrongly arrested by other Plumbers for interplanetary trespass.

In Darkstar Rising, Ben, Gwen and Kevin are forbidden to fight against the Highbreed threat by Magister Prior Gilhil, who doubts the Highbreed are as much of a threat as they are. However, all three sides find themselves working together when Darkstar captures them all but Gwen to feed his powers. With the help of the DNAliens, Gwen frees them and Darkstar is arrested while the Highbreed and the DNAliens escape. In gratitude, Prior Gilhil makes the team honorary Plumbers so they can defend the Earth legally. He also mentions that Ben's Omnitrix represents a Plumber Badge. It is also revealed that impersonating a Plumber is an interstellar-class felony. In War of the Worlds, all of the Plumber's Kids and Max participate in the final battle against the Highbreed. Notably, Gwen, Kevin, Cooper and Professor Paradox warped into the Plumber base in Mt. Rushmore to free Darkstar in order to participate in the battle.

As a result of Ben's defeat of Vilgax and neutralizing the Highbreed threat, as well as his status as Bearer of the Omnitrix, Ben holds a special status among the Plumbers ranks, even leading his own team.

At the end of War of the Worlds, Max recruits a team of Plumbers In-Training, with himself as both their leader and mentor. Max's team later fights and is defeated by Vilgax in Vengeance of Vilgax: Part 1. In Fame, it is revealed that all governments on Earth secretly recognize the  Plumbers organization in dealing with alien threats (explaining the existence of secret bases within Mount Rushmore and Fort Knox, as they were likely set up with the help of the United States government to aid the Plumbers).

In Escape From Aggregor, Prior Gilhil answered a distress call from Galapagus aboard Aggregor's Ship, only to be told by Aggregor on arrival that the distress call was a computer error. After demanding a search of the ship, he soon locates Aggregor's prisoners, only to be murdered by Aggregor. Aggregor stole Prior Gilhil's ship and suit.

In Too Hot To Handle, it is revealed that Plumber Badges can act as radiation detectors. At the end of the episode, Aggregor is shown attacking the Plumbers' ship which was carrying P'andor, the windows crack from Aggregor's attacks and throw the Plumbers into space, killing them.

In Deep, there is a place called Plumber Central Command and there is a Magister Plumber named Magister Pyke stationed on Piscciss.

In The Enemy of My Enemy, the Plumbers Academy had made an appearance and Magister Coronach is running the academy and he doesn't approve of the place being a prison or a battlefield.

In Basic Training, Ben, Gwen and Kevin are sent to a different Plumbers Academy where they were trained by Magister Hulka, the toughest Plumber of all.

In A Knight to Remember, a squad of Plumbers help Ben's Team fight the Flame Keepers' Circle in an attempt to capture Vilgax but failed.

Omniverse
The Plumber Headquarters beneath Max's Plumbing reappeared, where most captured villains are imprisoned if not imprisoned in the Null Void. The Plumbers have also seemed to gain control over in imprisoning certain humans if they proved to be a great enough threat as they captured Dr. Animo prior to It Was Them, Billy Billions in Arrested Development, and Nyancy Chan in Tummy Trouble.

Alternate Timeline
A group of active Plumbers based Bellwood is introduced in the movie Race Against Time. They have a secret underground base where the Hands of Armageddon was kept.

Ben and Gwen only came to the Bellwood base once.

The groups' main objective was to protect the Hands of Armageddon from Eon, which eventually entailed protecting Ben from Eon (who wished to use the Omnitrix to transform Ben into a younger Chronian, in order to use the Hands of Armageddon).

Known Plumbers in this movie included Hawkins the mailman, Fire Chief Whittington, Louise Dalton, Principal White and an unnamed old man.