玩家可以自行选择薛帕德在进入星联军队服役前的经历，by choosing either Spacer, Earth-born, or Colonist. This choice affects how others talk about the main character, and also modifies the rate at which Shepard gains Paragon and Renegade points. Some assignments in the game will only appear depending on the selected pre-service history.
- Spacer: Both of your parents were in the Alliance military. Your childhood was spent on ships and stations as they transferred from posting to posting, never staying in one location for more than a few years. Following in your parent's footsteps, you enlisted at the age of eighteen.
- Spacer characters gain a large bonus to 楷模 points received, allowing them to max out their Paragon bar faster.
- Spacer characters can have a short conversation with Hannah Shepard, the PC's mother, through an assignment that only appears with this background. (In both of the other backgrounds, Shepard's parents are deceased or otherwise absent.)
- Earth-born: As an Earth-born, you had a rough childhood in the slums of Earth, and have a gritty edge to your personality. You enlisted at the age of eighteen, in order to avoid falling into the trap of gang culture and poverty.
- Earth-born characters gain a large bonus to 叛逆 points received, allowing them to max out their Renegade bar faster.
- Earth-born characters also have a unique quest. A member of a gang Shepard belonged to in youth will approach Shepard outside Chora's Den in the Citadel Wards. Shepard is asked to help free a member of the gang from a turian in the bar.
- Colonist: You were born and raised on Mindoir, a small border colony in the Attican Traverse. When you were sixteen, slavers raided Mindoir, slaughtering your family and friends. You were saved by a passing Alliance patrol, and you enlisted with the military a few years later.
- Colonist characters gain a small bonus to both 楷模 and 叛逆 points received.
- Colonist characters also have a unique quest. When exiting the docking bay elevator, you will receive a request to help a fellow survivor of Mindoir, having been taken by slavers during the raid on Mindoir when you were sixteen.
在完成经历创建后，the player must choose a psychological profile: Sole Survivor, War Hero, or Ruthless - each of which relates to a specific event in Alliance history and places Shepard in a prominent role.
- 唯一幸存者：During your service, a mission you were on went horribly wrong. Trapped in an extreme survival situation, you had to overcome physical torments and psychological stresses that would have broken most people. You survived while all those around you fell, and now you alone are left to tell the tale. The Sole Survivor's unit was slaughtered in a thresher maw attack on Akuze.
- Sole Survivor grants neither Paragon nor Renegade points and affects the story of the UNC: Dead Scientists mission.
- 战争英雄：Early in your military career you found yourself facing an overwhelming enemy force. You risked your own life to save your fellow soldiers and defeat the enemy despite the impossible odds. Your bravery and heroism have earned you medals and recognition from the Alliance fleet. The War Hero almost single-handedly repelled an attack by batarian slavers on Elysium.
- War Hero characters gain bonus 楷模 points; this background slightly affects the dialogue of the UNC: Espionage Probe mission.
- Ruthless: Throughout your military career, you have held fast to one basic rule: get the job done. You've been called cold, calculating, and brutal. Your reputation for ruthless efficiency makes your fellow soldiers wary of you. But when failure is not an option, the military always goes to you first. The Ruthless character sent 3/4ths of his/her unit to its death and murdered surrendering batarians on Torfan.
- A Ruthless background adds bonus 叛逆 points and slightly affects the story of UNC: Major Kyle.
The player must then accept a military specialization, which determines a set of talents. The six classes are Soldier, Engineer, Adept, Infiltrator, Sentinel, and Vanguard. The class choice will also affect weapon proficiency - if Shepard is not proficient with a weapon, the commander can still fire it, but cannot zoom in with it, and many weapon bonuses are void. This applies to all weapons except the pistol, which all classes receive training in.
The player's choice of class does not affect the story in any way; there is only one minor variation in dialogue (when speaking to Kaidan Alenko) which refers to any chosen biotic class or biotic bonus talents.
If the player is creating a second character, at this point any unlocked bonus talents may be selected. These talents are unlocked by gaining the achievement for each talent. The player can choose one additional talent to add to their skill base. This talent is not reliant upon the existing class or prerequisite talents. For example, a pure Soldier can still have a tech bonus talent, and an Engineer could still be given Singularity without needing Warp. In the case the Soldier class is not chosen, the choice of a second weapon specialization such as the Sniper Rifle for the Adept, may be chosen instead of another ability.
The ultimate stage of customization, the player may alter their character's facial structure, head, eyes, jaw, mouth, nose, hair, scarring, make-up (female only) and beard (male only). Alternatively, the player may select the default appearance.
Before the game begins, a profile summary is shown for review, and a chance to return to previous stages of customization and make changes is available.
If Commander Shepard is not edited, and is accepted as stock, his name is John Shepard and will be an Earthborn, Sole Survivor and a Soldier.
在《质量效应2》预告中, Shepard's current status is given as "killed in action" over the image of bloodied N7 armor being worn by a geth. It has been suggested that this geth is Legion, because Legion has N7 armour as well, which it claimed to be Shepard's. It is revealed that just after the attack on the Citadel, the Alliance sent Shepard to root out geth resistance. The Normandy was sent into a sector where three ships were reported to have gone missing.
The Normandy is attacked by a Collector ship, ripping it apart. As the rest of the crew abandoned ship, Shepard went to rescue Joker. Unfortunately, a blast separated them, just as Shepard got Joker into an escape pod. The Commander's hardsuit was damaged by the blasts and was flung into space, barely surviving the Normandy's destruction. Air then began leaking out of Shepard's suit and it is apparent that the Commander suffocated to death, coupled with the possibility of the hardsuit burning up during entry to the planet below.
然而, in an effort undertaken by Cerberus called the Lazarus Project, Shepard is rebuilt and revived; organically and synthetically. Two years later, Shepard awakes in a lab to the Cerberus outpost being under attack. As Shepard moves through the outpost, the Commander begins to learn more about Project Lazarus and the effort taken to bring Shepard back - with many data caches citing the insane expense of the project and that, despite their efforts to make the Commander exactly as before, Shepard may have been inadvertently altered in some way. This information is likely presented to offer a suitable explanation if you had changed aspects of Shepard during reconstruction, whether it be physical differences or by changing class from the original Mass Effect save game. Shepard has also been referred to as "asleep" for some time by the Illusive Man, leader of Cerberus.
All the while, human colonies start disappearing during the Commander's incapacitation, so therefore, Shepard has to ally with Cerberus to solve this mystery. Meanwhile, rumors of Shepard's apparent survival have mixed concerns. Some would even think that Shepard is undercover investigating the colony disappearances.
Because Shepard was woken up before they were completely finished with the Commander's reconstruction, Shepard's face has several scars that can act as a visible indication of alignment. Gaining Paragon points will cause these scars to slowly fade, while Renegade points make the scars become more noticeable and somewhat frightening - these scars play a role in Shepard's ability to be more charming, or more intimidating. At the higher two sections of the Renegade scale, the eyes visibly glow red.
An email received from Doctor Chakwas shortly after Shepard has access to the newly constructed Normandy explains that the scars will heal on their own if Shepard uses "mind over matter" and has a "positive outlook" on the situation. It also states that surgery is possible to "insulate your cybernetic implants and accelerate your healing" through an upgrade done to the Normandy's Medical Bay. If the player chooses to have surgery done, the scars are permanently healed and Shepard's moral choices will no longer affect the Commander's appearance. (This upgrade costs 50,000 platinum.)
- Alan Bartlett Shepard, Jr. was the second person and the first American in space (May 5, 1961). He later commanded the Apollo 14 mission in 1971 and became the fifth person to walk on the Moon.
- 男性薛帕德的默认外貌是在荷兰模特Mark Vanderloo的面部基础上修改而成
- The female Shepard is played by prolific voice actress Jennifer Hale, who voiced Bastila Shan in BioWare's Star Wars: Knights of the Old Republic and Obsidian Entertainment's Star Wars: Knights of the Old Republic II - The Sith Lords, as well as Samus Aran in Nintendo's Metroid Prime series.
- When Shepard becomes inducted as a Spectre, according to Admiral Hackett Shepard is, technically, still part of the Alliance military (though Captain Anderson claims otherwise). Therefore, Shepard should still be referred to as a Commander, even though Shepard is outside of the Alliance military's chain of command and only answers directly to the Council.
- Military ranks can, in some situations, be deferred in favor of civilian ranks. Considering the nature of Spectres in the game, it is likely that is considered to supersede any military rank.
- Shepard's chosen pre-service history and psych profile plays a small background role in Mass Effect 2, over public announcement systems on various developed worlds (Illium, Omega, etc.)
- If Shepard is of the Earthborn background, a galactic news report will reveal the "Shepard Scholarship", an investment designed to give disadvantaged youths from Earth the chance to join the Alliance.
- If the Colonist background is chosen, a news report will reveal that Mindoir has succeeded in gaining the rights to use Shepard's likeness in their colonial seal.
- With the Spacer background, the news report will mention Shepard's mother, Hannah Shepard, rejecting an offer to become Admiral, she says that it's a political ploy and wants to best honor her fallen child's memory by remaining a Captain.
- If the War Hero background is chosen, the "Shepard Memorial Plaza" on Elysium has been voted the "hottest" place to get married.
- If the Ruthless background is chosen, there is a rush of attempts to extinguish Shepard's memorial flame on Torfan.
- If the Sole Survivor background was chosen, it will be announced that the Shepard Memorial on Akuze is scheduled to open in 2186, once the area is declared safe for visitors. Admiral Hackett will preside over the opening ceremony.
- 薛帕德的默认名字——男性为约翰（John），女性为简（Jane）——在英语文化中都是无名氏的代称（男性为John Doe，女性为Jane Doe）。
- It would appear that Shepard has a gift for being a leader. Miranda Lawson draws attention to this, claiming that Shepard has "that fire that makes someone willing to follow you into hell itself". This is similar to the protagonist of BioWare's Knight's of the Old Republic, who is also said to possess such an ability.
- To keep the exact nature of Shepard's return quiet in Mass Effect 2, it is often stated that the Commander almost died, which is not really truthful. The male Shepard would later joke with Jack that he is "technically undead".
- When stopped by a C-Sec officer on their first return to the Citadel in Mass Effect 2, one of the dialogue options has Shepard say that he/she was "only mostly dead." This may be a reference to Miracle Max's line from "The Princess Bride".