Plumbers

The Plumbers are a law enforcement organization that makes use of many high tech gadgets and weaponry to protect their planets in the Milky Way from various alien threats.

Ben 10
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 was a member in his youth and was ultimately the one who defeated Vilgax. Most of the organization itself has 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 Ben obtains the Omnitrix. Max uses his experience as a Plumber (along with various Plumber gear and weapons) to aid Ben.

In Big Fat Alien Wedding, it is revealed that the Plumbers have had a generations-long feud with the Sludgepuppies. However, when a close relationship was formed between Plumber Joel Tennyson (Max Tennyson's nephew) and a Sludgepuppy named Camille Mann, a truce was forged as a result of their relationship and their wedding was to be the first ever marriage between a Sludgepuppy 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 feud.

The Plumber's main base is located inside of Mt. Rushmore, where both the Null Void projector & the Sub-Energy are stored. In Truth, the Null Void projector was stolen by Phil (Max Tennyson's former partner) as part of a scam to profit from catching aliens he himself had released; however, his plan was thwarted by Max & Ben Tennyson. 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. Also, Max stated that there is one base built into every major millitary base in the country.

Three bases (Mt. Rushmore, the Space Needle and Fort Knox) were later attacked by Driscoll the Forever King (an Ex-Plumber who join the Forever Knights and over the years became the leader of the rogue faction) with the help of the Negative 10.

Ben 10: Race Against Time
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" were kept. Ben Tennyson and Gwen Tennyson only came to the Bellwood base once. The group's main objective was to protect the Hands of Armageddon from Eon, which eventually entailed protecting Ben Tennyson from Eon (who wished to use the Omnitrix to transform Ben into a younger version of Eon, in order to use the Hands of Armageddon). It is likely they disbanded after Eon was defeated and with the Hands of Armageddon destroyed.

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

Ben 10: Alien Force
In this series, the Plumbers are revealed to be an inter-planetary peace-keeping force, with both human & alien members.

However, Max Tennyson discovers that an alien race called the Highbreed and their minions, the DNAliens, are up to no good and he warns his superior, Magister Labrid (a fish-like alien) there is trouble brewing on Earth. The Magister quickly discovers Max has gone missing and mistakenly tries to capture Ben & Gwen (unaware that they are his grandchildren), believing they are responsible. Upon discovering who they are, he asks for their assistance in discovering the reason for Max's disappearance. The three of them manage to interupt an arms deal between the Forever Knights & the DNAliens, with Ben's old-rival, Kevin Levin (AKA Kevin 11) as the middle-man (or go-between). 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, Magister Labrid is fatally wounded. He 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 Plumbers' Badges bear the intergalactic symbol for peace. There is also a practice where alien Plumbers who have inter-bred with humans give their hybrid-offspring a Plumbers' Badge to prevent them from being arrested by other Plumbers for interplanetary trespass. They are generally refered to as "Plumbers' Kids".

In Darkstar Rising, Ben, Gwen and Kevin are forbidden to fight against the Highbreed threat by Magister Prior Gilhil, the commanding officer for the sector that includes Earth, who doubts the Highbreed are even as much of a threat as they claim. However, all three sides find themselves working together when Mike Morningstar, AKA Darkstar, captures all but Gwen to feed his powers. With the help of the DNAliens, Gwen frees her friends and Mike is captured while the Highbreed Lord and the DNAliens escape. In gratitude, Magister Gilhil makes the team Honorary Plumbers so they can defend the Earth legally. He also mentions that Ben's Omnitrix can also represent a Plumber's Badge. It is also revealed that impersonating a Plumber is an interstellar-class felony.

In the second season finale War of the Worlds: Part 1 and War of the Worlds: Part 2, all of the plumber's children and helpers (including Max Tennyson) participate in the final battle against the Highbreed and the DNAliens. Notably, Gwen, Kevin, Cooper and Paradox warped into the former plumber base in Mount Rushmore to free their enemy Darkstar in order to participate in the battle.

As a result of Ben's defeat of Vilgax & 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 Vendetta, it is revealed that Kevin's father, an Osmosian Plumber named Devin Levin, sacrificed himself to save Max and prevent Ragnarok from destroying Earth's sun.

Ben 10: Ultimate Alien
In Fame, it is revealed that all governments on Earth secretly recognize The Plumbers organization in dealing with alien & paranormal threats (explaining the existence of secret bases within Mount Rushmore & Fort Knox, as they were likely set up with the help of the United States government to aid the Plumbers).

In Escape From Aggregor, Magister Prior Gilhil answered to a distress call aboard Aggregor's ship, only to be told by Aggregor on arrival that it was a computer error. After demanding a search of the ship, he soon locates Aggregor's prisoners, only to be attacked from behind and killed by Aggregor himself as he began reciting the present violation. Aggregor is shown later wearing Ghilhil's uniform.

In Too Hot To Handle, it is revealed that the 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 appearence and Magister Korwak is running the academy and he doesen't approve of the place being a prison nor a battlefield.

In Basic Training, Ben, Gwen and Kevin are sent to one of the Plumbers Academies where they ended up being trained by Magister Hulka.

Plumbers' Kids
Most Plumbers' kids are hybrid offspring of various alien members of the Plumbers, fully human or their alien heritage does not show any physical signs.

Trivia

 * Apparently, dual-wielding plasma pistols during gunfights is authorized under Plumbers' laws.
 * There are Plumbers who don't battle or arrest. Some of them, like Galvan plumbers, are teachers or scientists.