Professor Paradox

Professor Paradox is a time traveling professor who can travel anywhere in space or time, within reason. While he forgot his true name from centuries being trapped in a separate reality, he now goes by the name "Professor Paradox," after taking a liking to being referred to as such.

Personality
Paradox is portrayed as a calm, easy-going man. He talks much like a stereotypical scientist, with dialogue requiring a greater command of the English language to fully understand. When he was displaced outside of time, he went crazy; however, millennia later, he "got bored of that" and became sane.

In his first appearance, Swampfire tried to capture Paradox (not knowing whether he was friend or foe), but he always "teleported" to a place a few meters away. When Swampfire asked how he did that, the calm Paradox replied: "It's called walking". He really likes gumballs and is often seen offering to anyone he meets.

Paradox has a habit of getting events that haven't happened yet (from the perspective of the viewer and those he's talking to) and those that have (from his perspective) mixed up, due to his travels through time.

Paradox's calm personality also makes it difficult to tell when he's joking or not, such as telling Kevin that if his replacement car (factory new from the past) came in contact with anything else from the same year it was made, it would "explode like anti-matter."

Background
At some point he was working for Area 51. It's not known what his job was exactly, but it had something to do with the alien prisoners there.

In the 1950's, Paradox, having discovered special properties in quartz crystals, received government funding to break a hole in the space-time continuum. However, a slight miscalculation, and an explosion accidentally caused by his panicked assistant Hugo, threw Paradox into the event horizon, where he remained for a hundred thousand years. He was displaced outside of time, where he didn't age, or have to sleep or eat; just exist. He went insane for a while, but then got bored and regained his sanity. He gained complete understanding of the space-time continuum, though he forgot his original name in the process.

Alien Force
Paradox used his understanding to travel across time, making different parts of history better for others. He said he would help Ben save the "whole entire universe".

Paradox soon learns that the accident sent an extra-dimensional creature fifty years from the time of the experiment. He traveled to the Alien Force time to stop it, meeting Ben's younger self. It was at this point that he gained his new moniker, with Gwen bringing it up as the name of his original time travel project. After a few fights with the creature, Ben told Paradox to take them all back to the accident, where it is discovered that Hugo was the creature. He was frightened and confused, but turning everything to dust. By preventing Hugo from being sucked into the event horizon, it negated his time-accelerating existence. After returning to Ben's present, Paradox was stoked that he didn't see it in the first place. He took an older Hugo to a behind-the-scenes look at eternity.

Paradox left the trio one last gift, Kevin's regressed car, factory new from 1976. But a note warns him that if the car comes in contact with anything from that era, it would explode like antimatter. Dwayne McDuffie has confirmed that the note that Paradox left Kevin was merely a joke.

Paradox returns in the two part season two finale, War of the Worlds. He meets up with Azmuth, who greets him as "Time Walker", just as the Highbreed begin to invade Galvan Prime. Paradox convinces Azmuth to escape the planet's destruction, before meeting up with Ben. He informs Ben of the impending crisis, who resorts to gathering all the allies he made. Paradox aids Gwen and Kevin in recruiting Alan, Cooper and Darkstar to help in the fight, by teleporting them to the right location. He then joins Ben's Team and partakes in the following battle against the Highbreed. Here he displays the ability to slow down time using his watch, allowing him to move at high speeds and taking out a large number of DNAliens. Later he accepts a gun made by Cooper and uses it to turn DNAliens back into humans.

Paradox appears in Time Heals where he tries to stop Gwen from traveling back in time to stop Kevin from mutating, but is unable to persuade her. After Gwen succeeds in her endeavor, she returns to the present to discover a post-apocalyptic world enslaved by Hex and Charmcaster. Paradox appears again and informs her that she is the cause of all this, as well as telling her that "time traveling is for immortals and fools". He brings Gwen up to date with the events of this alternate future, which end up with Ben getting captured, Kevin becoming enslaved by Charmcaster, and Gwen being killed. A shocked and guilt-ridden Gwen attempts to repair the damage she has done, to which Paradox cautions her to be careful, only to discover she has already left. He smiles knowingly and states that "youth never listen". After Gwen manages to retrieve the book with the time travelling spell, and manages to fix her mistake, Paradox appears once again in the restored present. Gwen asks him whether there was any more trouble, to which he states there wasn't before mysteriously vanishing again.

Ultimate Alien
Paradox appears in the episode of Ultimate Aggregor by giving advice to Kevin. It is revealed he divided the Map of Infinity into four pieces in the past.

In Perplexahedron, it is revealed Paradox created the planet Perplexahedron to hide the final piece of the map from those who would misuse its power.

Paradox appeared in The Forge of Creation, having the key to stop Ultimate Aggregor from tapping into the power of Alien X by helping Ben and his team getting there and he also took 10 year old Ben home. Paradox also can't be within 500 light years of any Celestialsapien, although why he isn't allowed to go near them is currently unknown.

Paradox appeared in Ben 10,000 Returns to visit Ben 10,000 and helps Ben 10,000 and Ben's Team foil Eon's evil plan. At the end of the episode, he asked Ben 10,000 to restore Swampfire and Way Big. He also gives a warning to Ben's team about Old George and the Creature From Beyond before leaving with Ben 10,000.

Omniverse
Paradox has already been aware that the the universe had been destroyed in So Long, and Thanks for All the Smoothies, and replaced with a near-identical one by Alien X. In the flashback of Blukic and Driba Go to Area 51, he was called by Colonel Rozum to help with the investigation about Blukic and Driba's fall on Earth.

Sometime in his life, Paradox was busy fighting in a Time War, apparently losing his right hand and replacing it with a robotic prosthetic. He had disguised his Chrono Navigator (his pocket watch, noted as a "GPS to the multiverse") for safekeeping,

Paradox managed to trap Eon in the Main Timeline to prevent him from crossing into others to cause chaos.

Paradox returns in Ben Again, where he's lost his professor look and now has, as Ben describes it, a Steampunk general look. Following Eon switching the minds of 11-year-old Ben and 16-year-old Ben, Paradox goes fives years into the past to talk with 16-year-old Ben following Max's warning him not to give spoilers about the future. He informs Ben of his involvement in the Time War are the reason for his missing hand and that he has gone to great lengths to prevent Eon from causing havoc.

However, Eon finds him and cuts off his right hand, which is actually his disguised pocket watch, and takes him to an alternate dimension to be interrogated. As he is not a liar, Eon knows he doesn't have the Chrono Navigator with him and goes to take it from 11-year-old Ben. When Eon begins to use the Chrono Navigator to bring his minions into the main timeline, time begins falling apart. He is freed from his shackles thanks to 11-year-old Gwen and 16-year-old Gwen. Instructing both Bens to use Clockwork to place Eon between both periods of time, the timeline is restored to normal and all memory of the event is erased.

Ben 10,000 later comes looking for Paradox in 16-year-old Ben's era, saying that the Chronosapiens have gone rogue and Maltruant's beasts are on an inter-dimensional rampage, said this time war is getting out of hand.

In And Then There Were None, Paradox learns that Eon and Vilgax are abducting and brainwashing alternate Bens into serving them. He and Ben Prime travel to No Watch Ben's timeline, and are surprised that there is no Omnitrix in that Universe. They are confronted by Vilgax and Eon's evil Bens, who are countered by several alternate Bens. As the battle rages, Paradox vanishes, returning only after Vilgax sets off a Chronosapien Time Bomb, wiping out every timeline but No Watch Ben's. Paradox pulls No Watch Ben out of Vilgax's grasp, and tells him they have to restart Ben Prime's timeline.

In And Then There Was Ben, Paradox brings No Watch Ben to Vilgax's ship on the day Ben Prime found the Omnitrix, and directs him to ensure events happen the way they originally did. With that done, they begin recruiting the alternate Bens for the previous battle against Vilgax and Eon. Paradox leaves No Watch Ben behind, then returns to send him to the moment after he pulled him away from Vilgax. When the villains are defeated, Paradox returns all the alternate Bens to their own timelines.

In Let's Do the Time War Again, he and Ben 10,000 come to the present to find that time has stopped (due to a clash of energies between Feedback and a Time Beast). They travel further back in an attempt to prevent this from happening. They rebuild the wreckage of Rook's Proto-TRUK and Ben's Tenn-Speed into Time Cycles, using them to save Ben and Rook when the battle with the Time Beast goes awry once more (creating a black hole). They travel back to the same time as before, where Ben and Rook aid their past selves, and use their Time Cycles to revert the Time Beast back into an egg. Paradox takes the past Ben and Rook back in time to "close the loop."

In Secret of Dos Santos, Paradox appears to Ben, Rook and Kai Green in The Temple of The Sky, revealing that the artifact they'd been seeking was one of Maltruant's parts, which Paradox had scattered through time after Maltruant's defeat. The part they found was the main spring, which Paradox had hid in the temple years ago, under the protection of Ujin. When Exo-Skull attacks, Paradox tells Kai he can't do anything. After Exo-Skull is defeated, Paradox takes Ujin back home.

In A New Dawn, he gives Ben and Rook a Time Beast egg, which powers up their Time Cycles enough to follow Maltruant to a place even Paradox cannot reach: the beginning of the universe. Following Maltruant's defeat, Paradox reveals that the villain is unknowingly trapped in a time loop, doomed to be defeated again and again, with Paradox hiding his parts each time. Paradox asks Ben and Rook to help hide Maltruant's parts before he returns them home.

Powers and Abilities
Due to his time in entrapment for several millennia, Paradox has a working understanding of the space-time continuum. This allows him to travel to any point in space and time, as well as slowing down or speeding up time as he pleases. However, he states that there are places he cannot go and things he cannot do, though what restricts him is not yet explained. Paradox's abilities are not limited to this universe, having visited other universes and the space between them.

Paradox is able to regress a person's age, but seems incapable of doing it on something mechanical, instead having to pull it physically out of the past.

Paradox is capable of teleporting people, objects and even places like the Forge of Creation to almost any destination instantaneously without any trouble. However, he does have to follow certain rules; for example, he cannot bring the past and future versions of an individual together unless absolutely necessary.

Additionally, Paradox's time travel powers have left him biologically immortal, with no need to eat or sleep.

Paradox is capable of reverting Ben from an alien back to his human form as he did to Alien X in The Forge of Creation.

Weaknesses
There are places in existence Paradox cannot reach with his powers, such as before the beginning of time.

Paradox had admitted that he does not lie and Eon has confirmed this.

Getting control of Paradox's Chrono Navigator might give one an advantage over him, though this has proven to be a double-edged sword, as Eon almost destroyed all reality.

Ben 10: Alien Force

 * Paradox (first appearance)
 * War of the Worlds: Part 1
 * War of the Worlds: Part 2
 * Time Heals

Ben 10: Ultimate Alien

 * Ultimate Aggregor (first re-appearance)
 * Map of Infinity (flashback)
 * The Forge of Creation
 * Ben 10,000 Returns

Ben 10: Omniverse

 * Ben Again (first re-appearance)
 * And Then There Were None
 * And Then There Was Ben
 * Blukic and Driba Go to Area 51 (flashback; cameo)
 * Let's Do the Time War Again
 * Secret of Dos Santos
 * A New Dawn

Ben 10 Alien Force: Vilgax Attacks
Paradox appears in the Ben 10 Alien Force: Vilgax Attacks video game. He first appears during the alien invasion telling Ben that it is not the time to use Alien X. After Azmuth's visit to Ben, Paradox returns and rewinds time to the point before the alien invasion. Paradox even helps Ben escape from Anur Phaetos. After Ben defeated Vilgax, Psyphon steals the energy core to power up the Null Void Projector, Paradox then appears and tells Ben that it is time to use Alien X.

Punch Time Explosion XL
During the first Ben 10 level in Bellwood, Paradox makes a cameo in the game.

Trivia

 * Due to the nature of his abilities, it is difficult to tell exactly what order the events of the series take place, from his perspective. During his introductory episode he was already familiar with Ben, Gwen and Kevin, and later events in the series. His first meeting with them (from his perspective) has yet to be seen.
 * Dwayne McDuffie confirmed that Professor Paradox was inspired by The Doctor (especially the Tenth Doctor) of the British television show Doctor Who.
 * The pop-up trivia version of Ben 10: Race Against Time states that Paradox also stopped Eon prior to the events of the film.