Lal was a female Soong-type android constructed by Data in 2366 on the USS Enterprise-D. She exceeded her "father"'s abilities in several ways, notably by being able to complete more than sixty trillion calculations per second, using contractions, and feeling emotions such as fear and love.
Conception and creation Edit
The idea to create Lal came when Data attended a cybernetics conference, where he learned of a newly-developed submicron matrix transfer technology. Using his own positronic brain as a template, Data thereby programmed the brain of the android that would ultimately be known as Lal. His initial tests proved successful, leading him to continue his project.
Lal's creation allowed Data to accomplish two things – to re-create the work of his "father", Noonian Soong; and experience the act of procreation and thusly having a family. Data chose the name for his offspring from the Hindi word meaning "beloved".
Data's eventual hope was that someday Lal would enter Starfleet Academy and serve in Starfleet, as he had. He wished to give back to the organization that had given him so many opportunities. Regardless, he felt that ultimately, it was his role to parent her, not Starfleet's.
Originally genderless and possessing a very basic humanoid appearance, Lal was allowed to choose its own gender and appearance. Lal originally wished to share Deanna Troi's gender and features, but Data discouraged the move, saying it would be confusing.
After narrowing the choices to four – an Andorian female, a Human male and female, and a Klingon male – Lal chose the Human female form. Additionally, she was given a skin pigmentation and eye type consistent with Human females, as opposed to Data's less Human features.
Becoming Human Edit
Data wanted her to learn about "being Human", and per Wesley Crusher's suggestion, enrolled her in the ship's school. Unfortunately, she was not able to socially interact with the older children, who were closer to her level of intelligence, and the younger children were afraid of her. When discussing her interactions with the children, Lal believed she had unintentionally made jokes, saying they had laughed at her remarks. Data explained that they were laughing at her, not with her, mainly because she was different from them.
Data then sought parental advice from Beverly Crusher, explaining he did not know how to help Lal with her realization that she was different from other people. Crusher suggested that he share his own experiences to encourage her, something he had not done, believing that it would only discourage her instead.
Data then decided that allowing Lal to work in Ten Forward would give her more valuable insight into Human social interaction. She was mentored by Guinan, who tried to answer all of her questions, but left matters of sex for Data to answer. While working in the bar, Lal began to improve on her father's original specifications, becoming able to use verbal contractions and even, eventually, to feel emotions. Her knowledge of proper behavior and timing was still lacking, however; after observing a couple's romantic interactions, she hauled an unsuspecting William T. Riker up off the ground and kissed him, despite the two having only just met each other.
A proposed separation Edit
When Starfleet Research and Development learned of Lal's existence, Vice admiral Anthony Haftel attempted to separate Lal from Data in order to study her closely. Aghast at the idea of her working in Ten Forward, he believed the Daystrom Institute annex on Galor IV would be a better environment for her. Lal was then interviewed by Haftel, and agreed that his facilities would be beneficial to learn, but only after having completed her learning aboard the Enterprise with her father.
The situation caused Lal distress, and while speaking with Deanna Troi, she began to feel fear over her impending separation from her father. Her programming perceived a malfunction, causing her to return to the Enterprise lab, as she had been programmed to do in the event of a problem.
Upon running diagnostics, Data identified the problem as a symptom of a cascade failure in her neural net. With the assistance of Admiral Haftel, he attempted to repair the damage. However, despite their best efforts, the effect was irreparable, and Lal's neural net failed.
Haftel described the experience to a waiting LaForge, Troi, and Wesley Crusher: "There was nothing anyone could have done. We'd repolarise one pathway and another would collapse. And then another. His hands were moving faster than I could see, trying to stay ahead of each breakdown. He refused to give up. He was remarkable. It just wasn't meant to be."
As Lal lay dying, she expressed her love for her father and thanked him for creating her, before summing up her brief life in a few short words. She succumbed to complete neural system failure at 1300 hours, after which Data deactivated her.
Interestingly, the symptoms of Lal's shutdown achieved something Data had been trying to achieve for many years: basic Human emotions. It would be five more years before Data would achieve the same results in himself, and this only after implanting a new chip created by his "father". Though also suffering a neural net failure as a result, Data recovered and was able to function normally afterwards, even able to toggle the ability to feel emotion on and off at will. (TNG: "Brothers"; Star Trek Generations)
Understandably, Lal remained in Data's thoughts for many years after. During his experimentation with painting, Data painted a portrait of Lal, which he later showed to Juliana Tainer – essentially, Lal's 'grandmother' – when she visited the USS Enterprise-D in 2370. Despite her unfortunate death, he still wished to procreate again some time in the future. (TNG: "Inheritance")
Lal's other potential bodies Edit
"She is capable of running over sixty trillion calculations per second, and you have her working as a cocktail waitress."
- - Haftel, on the perceived misuse of Lal
- - Lal's dying words
Background information Edit
- On the makeup used: "For Lal, makeup designer Michael Westmore did a plaster cast of my entire body, done in sections. The body of the costume consisted only of latex buns and an angular bra that was glued on, plus metallic contact lenses. The rest was naked me sprayed with metallic gold paint. Then Michael did his wonderfully creative sculpturing of the face in latex. I was very honored to read that Michael Westmore considered it one of his best efforts."
- On being Lal: "Lal was a fantastic part because I got to play an entity that wasn't fully formed. I was the child of Data, so I needed to be a bit like him in my movement and yet also a child that is a separate being with its own life. And I had to do this mostly without dialogue. The story is profoundly tragic; the loss of a child is the worst loss. I have received wonderful mail from Next Generation enthusiasts and it tells me that the story is universal. I'm proud to be a part of it all."
According to Makeup Man: From Rocky to Star Trek, Crofoot once spent a full fourteen hours inside the Lal prototype suit without eating or drinking in order to avoid having to use the bathroom while wearing his costume. 
Although stated in the episode (TNG: "The Offspring") that Lal means 'beloved' in Hindi (a derivative word of Persian and Urdu), it is not the only definition. Lal means 'red', in the Indo-Iranian context, while in the Indian context, it means 'child' or 'beloved'.(citation needed • edit)
The writing staff on TNG considered bringing Lal back in an unproduced fifth season episode, wherein Lore would return, steal Lal's remains and try to revive her with Dr. Soong's emotion chip, but it was rejected for unknown reasons. 
In the short story "The Embrace of Cold Architects" by David R. George III, collected in the Star Trek: Myriad Universes anthology Shattered Light, Lal's creation was delayed after Data missed a vital scientific conference until the return of the Borg, allowing Picard to 'distract' the Borg by focusing on Lal and the long-term implications of her existence after he became Locutus of Borg, allowing Riker time to give the order to destroy his Borg cube and kill Locutus before the Borg could find and adapt to their attack. Lal's subsequent breakdown was then averted by the intervention of Doctor Noonien Soong when he 'summoned' Data to him, Soong's expertise allowing him to repair the damage to Lal's neural net. With the information of how to create stable androids, the Federation began creation of a new race of android soldiers intended to fight the Borg, but Data is able to destroy their prototypes.
In the novel Cold Equations: The Persistence of Memory, it is revealed that Lal's remains are kept at the Daystrom Institute, along with the remains of her 'uncles'; Soong's three original prototypes, B-4, and Lore. She is briefly stolen by the Breen, but is recovered thanks to the Enterprise-E and Doctor Soong – still alive after transferring his mind into an android body – who subsequently manages to restore Data. Data then resolves to find the mysterious immortal known as Flint – based on reports that Flint was responsible for reactivating Juliana Tainer after her positronic net shut down, hoping that Flint will be able to help him restore his daughter.