Before the first Mega Man game
In the 20th century, Thomas Light attended the Robot Institute of Technology (ローバート工科大学Robert Institute of Technology) where he met Albert W. Wily and became classmates. The two graduated together with their doctorate degrees (PhDs), although Light always received more credit than Wily. The two were nominated for the Nobel Prize for physics, but only Dr. Light won. Dr. Wily, with his pride hurt and tired of being in second place, vanished, and Dr. Light didn't see him again until the events of the first game. At an unknown time, Dr. Light (alongside Dr. Wily in some sources outside of Japan) founded his laboratory to further the development of computing and robotics technology for the benefit of mankind in the coming era. Light became a world-renowned scientist and the leading expert on robotics.
Light built a series of household and civil service robots. Not long after that, he created a humanoid robot with a much more advanced A.I., DLN-000 Proto Man, the first "advanced robot", known as a Robot Master in some sources. However, Proto Man's dangerous imbalance in his energy core and having a strong sense of independence, went A.W.O.L. before his repairs were complete in fear that Dr. Light would change his personality in the process. Yet, in the year 200X (sometime in the first decade of the 21st century), Light would build on the successes and failures of the Proto Man project to build other Robot Masters, like Mega, Roll (a householder), and a series of industrial robots.
When Dr. Wily grew jealous of Light's works receiving credit and his works not (in USA sources he's jealous because Light received all the credit for the team's work), he stole and reprogrammed Light's industrial robots, attempting to take over the world. Rock, having a strong sense of justice, volunteered to be converted into the super robot known as Mega Man.
Mega Man Games
After converting Rock into Mega Man, Mega Man fights against Dr. Wily's forces and manages to defeat him. After Wily's first defeat, he tries to conquer the world again several times, and Dr. Light has been developing new inventions to help Mega Man counter Wily. Some of his main creations include Items 1-3, Rush, Eddie, Tango, Auto and upgrades to the Mega Buster.
In most games, Dr. Light only appears in scenes, some of them being brief. Below are all his appearances in the games:
- Mega Man: In-game, Dr. Light only appears in the ending alongside Roll. In the Rockman Complete Worksversion, he is also the Navigator from the Navi Mode.
- Mega Man Powered Up: Dr. Light stays in his laboratory alongside Roll.
- Mega Man 2: Dr. Light appears to he gives Items 1-3 to Mega Man.
- Mega Man 3: Dr. Wily pretends to be sorry for his acts and works together with Dr. Light to build the giant peace keeping robot Gamma. They also created some Robot Masters together so they could obtain the Energy Elements needed to complete Gamma. When Gamma was near completion, Wily stole it to be used in his plans to conquer the world, but Mega Man manages to destroy Gamma. Dr. Light realizes that the robot who rescued Mega Man in the ending is Proto Man.
- Mega Man 4: While Dr. Light has no appearances in-game, he improved Mega Man's Mega Buster, allowing Mega Man to fire charged shots, and he created the support robot Eddie.
- Mega Man 5: Light was captured by Proto Man (Dark Man 4) at the beginning of the game, and was rescued in the ending.
- Mega Man 6: Dr. Light is absent in-game, but he modified Rush so he can combine with Mega Man, changing him into Power Mega Man or Jet Mega Man. He is the Navigator from the Navi Mode in the Rockman Complete Works version of the game.
- Mega Man 7: Light appears in the opening stage, in his lab, and in the ending. When Bass was damaged by Shade Man, Mega Man said Dr. Light could repair him. After his repairs, Bass attacked the lab and stole plans that Light created to improve the Rush Adapter. Wily used the plans to create the Super Adapter for Treble.
- Mega Man 8: Dr. Light asks Mega Man to investigate an outer space object that had fallen on an island, which coincidentally was being used by Wily as a hideout. Wily gets to the crash site first and collects the "Evil Energy" before fleeing the scene. Unable to halt Wily's escape, Mega Man discovers and retrieves a heavily damaged robot from the crater called Duo. Light repairs Duo and studies a small portion of the Evil Energy that was found. After Mega Man defeats four Robot Masters, Duo awakens and destroys the Evil Energy in Light's laboratory, and goes after the Evil Energy in Dr. Wily's possession.
- Mega Man & Bass: Dr. Light appears in the CD database to say how the collection is going and as one of the database's entries. He also appears in Mega Man's ending.
- Mega Man 9: Light is charged for the crimes committed by his robots and is sent to jail, but when it was discovered that Wily reprogrammed his robots, he is freed. Dr. Wily also used a Light-like robot to create an incriminating video. In the ending, Dr. Wily uses the fake Dr. Light to trick Mega Man into believing that Light was taken by fake officers and felt ill while in his Wily Castle.
- Mega Man 10: Dr. Light appears in his laboratory, where he takes care of the ill Roll and works with Wily to find a cure for Roboenza.
- Mega Man IV and Mega Man V: Dr. Light exchanges P Chips by items in his laboratory.
- Wily & Right's RockBoard: That's Paradise: Dr. Light is a playable character. His objective is to expand his facilities, making world peace easier to achieve.
- Mega Man: The Wily Wars: In order to stop Dr. Wily's alterations in time, Mega Man was sent into the past in a time machine hastily crafted by Dr. Light.
- Mega Man's Soccer: Dr. Light was watching a game of soccer on TV with Rock and Roll. When Dr. Wily's robots attack the field, Light modifies Mega Man so he can face the robots.
- Mega Man: Battle & Chase: As Dr. Light's super computer was damaged due to a thunder storm, Mega Man decides to enter the Battle & Chase tournament and use the prize money to buy a new computer. In Mega Man's ending, Dr. Light says he repaired his computer, and the money is used to throw a party to commemorate Mega Man's victory.
- Super Adventure Rockman: Dr. Light immunizes Mega Man, Rush, Beat and the six industrial Robot Masters from the first game from the electromagnetic waves caused by Ra Moon, and watches over Roll while they try to stop Wily.
- Mega Man: The Power Battle: Dr. Light appears in Mega Man's ending.
- Mega Man 2: The Power Fighters: Dr. Light appears in the endings of Mega Man, Proto Man, and Duo. In Mega Man's ending, he cheers up Mega Man alongside Roll and Auto. In Proto Man's ending, Light is worried with Proto Man and tries to convince him to repair the defect in his energy system, without success. In Duo's ending, Light talks with Duo about a strange alien energy and bids him farewell.
- Rockman & Forte: Mirai Kara no Chousensha: Dr. Light is the shopkeeper in Mega Man's story.
- Mega Man Rush Marine: Dr. Light appears in his laboratory.
In the year 20XX (later in the 21st century), Dr. Light began work on Mega Man X (the "X" standing for a factor of unknown potential). X would possess the ability to make his own decisions in life, unlike Rock who was bound by Asimov's "laws of robotics". However, Light knew that he would not live long enough to fully test X's potential, so he had X sealed in a capsule on September 18, 20XX, not to be awakened for thirty years. He is presumed to have passed away some time after.
Mega Man X Series
In 21XX, more than 30 years after X's seal, Dr. Cain found the capsule with X in the ruins of Dr. Light's Laboratory. A holographic image of Dr. Light continued to provide support for X through the use of capsules during the Maverick Wars. This image of Dr. Light is shown to be able to keep up with current events and communicate with others. In Mega Man X5's ending, Light is shown to be able to appear outside the capsule, although it only happened once to repair a fatally injured X. It is unknown if Light can willing appear outside the capsule or was only able to do so due to the effects of Zero Space.
Other video game appearances
- Dr. Light, along with Dr. Cossack, is responsible for creating the Reploid OVER-1, the main protagonist ofRockman ×over. Dr. Light appears in some of the game's Battle Memory.
- Dr. Light made short appearances in Marvel vs. Capcom: Clash of Super Heroes and Marvel vs. Capcom 2: New Age of Heroes in Mega Man's and Roll's victory poses, and in Roll's ending from Marvel vs. Capcom andTatsunoko vs. Capcom. He also has brief appearances in Capcom World 2.