Adorkable: Not on his father's levels, but he still has his moments. Like in Part III when he realizes that he's alone with a gun, and decides to start pointing it to his reflection and mimics Robert De Niro and Clint Eastwood. All while he's wearing pajamas.
Badass: Particularly the way he handles 1955 Biff Tannen.
Berserk Button: "Nobody calls me chicken!" This ends up getting him into an accident the day he returns from 1885. (May also qualify as a Noodle Incident, since it didn't appear in the first movie. Though that may just be a coincidence.)
He also hates it when his friends or family are being abused. Especially by Biff.
Beware the Nice Ones: He's very sweet and friendly, but he still has a hell of a right hook and won't hesitate to use it.
Book Dumb: Seems to actually need the exposition Doc gives... but it seems to have been him that hooked that 1985 video recorder up to Doc's 1955 TV. Maybe Doc's been teaching him?
In Part III, Marty finally overcomes his Fatal Flaw/Berserk Button, saving himself from getting killed by Buford Tannen and saving himself from becoming a Future Loser by never agreeing to the street race with Needles.
Chekhov's Skill: Skateboarding, guitar shredding, and (later) arcade shooters.
Combat Pragmatist: Kind of necessary when facing guns and men twice your size (sometimes both at once).
Compressed Vice: Again, his dislike of being called a chicken. In the second movie, his parents reflect on how this was always his Fatal Flaw. Would be normal if it weren't for the fact that he isn't shown to have this trait in the first movie; he has a quick temper and some Determinator aspects, but no one calls him out on anything directly.
Future Loser: Part II reveals that Future Marty gave up guitaring and ended up a lowly salaryman, stuck working for his high school enemy (à la George). Luckily in Part III, Marty manages to avert the event that led to this timeline, with the implication that he has a better future.
Future Badass: If the ending to the Telltale game can be trusted.
Guile Hero: He uses his wits as much as his physical ability to solve his problems.
High School Hustler: Downplayed. He's not really a trickster as usually seen in this trope, but he's no less lucky and helpful. Played straighter in the early drafts for the movie, however.
Hypocritical Humor: In the first movie, Marty takes away Lorraine's liquor bottle, saying that she may regret it later in life. He then immediately starts to drink from it himself, but spits it out when Lorraine starts to smoke.
Kid from the Future: In Part I. Technically a "Great-Great-Grandkid from the Future" in Part III.
Look Behind You: Not only does Marty love this, but it almost always works!
Loser Son of Loser Dad: In the first film, Strickland sneers that Marty comes from a long line of SLACKERS. (Which is unfair, as he's clearly more outgoing than George ever was in the original timeline.)
Love at First Sight: Says that this happened with him and Jennifer when Doc scoffs at the idea.
Pride: The proper name for his Fatal Flaw. He feels he can't back down from a challenge when called "Chicken", but as the series goes on this turns out to have serious and by part III, near fatal consequences. Eventually he learns to overcome it after some sound advice from his ancestors. Which inadvertently saves his future in the process.
Scars Are Forever: In the game, when trying to prove to his parents that he really is their son in an alternate timeline note (as the Marty in that timeline has been run out of town) it's revealed that he has a scar on his left knee that he got in a skateboarding accident when he was twelve.
A Real Life example happened in a blooper of the same scene - as a prank, the prop bottle was replaced with an identical one with real alcohol in it, causing Michael J. Fox to spray it all over himself and hilarity to ensue.
Supporting Protagonist: Word of God views him as this in the first and third movies, with George and Lorraine getting the most development in Part I, and Doc getting it in Part III.
This Is Wrong on So Many Levels: Marty often reacts like this when stuff happens with his young mother and grandmother too in the game, for different reasons.
Tragic Hero: Narrowly subverted; his Fatal Flaw nearly causes him to break his hand and ruin his rock star dreams in a race with Needles or get shot by Buford, but he learns to overcome those flaws and therefore doesn't fall into tragedy.
True Companions: To Doc. In the movies, yes. But it's especially flagrant after the game.
The Watson: Neither unskilled nor unintelligent, but can't hold a candle to Doc.
Adorkable: Especially in Part III, when he sees Clara at the dance.
Age Lift / Dawson Casting: Christopher Lloyd was only 48 when he filmed the role for the 71 year old Doc Brown. Probably done on purpose so when Marty goes back to 1955 and meets the 41 year old Doc Brown they look the same, except for aging make-up in 1985, which was dropped in the other parts as Doc underwent a rejuvenating process. They also replaced his spleen and colon.
Character Development: Goes from believing at the start of the trilogy that "no man should know too much about his destiny" to saying that "the future hasn't been written yet. No one's has. Your future is whatever you make it!" at the end.
Deuteragonist: Although, Doc is arguably the main character of the third film.
Einstein Hair: How did he get his hair to stick out like that? The game expends on this. During the 1931 HV Science Expo. Young Emmett is driving his flying rocket powered car, which explodes violently. When Emmett exits the expo, his hairs became like his movie counterpart, as a result of the explosion (which he didn't have before). He comments that after that incident, he got banned from the expo for at least 50 years.
Indy Ploy: More subtly than Marty, but Doc can be surprisingly pragmatic when he needs to be.
Intergenerational Friendship: It's a credit to the actors that we, as viewers, don't question why a skater punk and some old guy would hang out together.
The original script had a line by Marty explaining that Doc hired him to clean his garage. Marty, being a music aficionado, was impressed with Doc's vintage record collection. The rest is history.
The screenwriter decided it wasn't necessary to explain how they first met. Doc is a local pariah and a weirdo, and Marty is clearly a rebel. It's inevitable that Marty would snoop around Doc's garage at some point.
Another explanation could be drawn from the movie - that their friendship is a Stable Time Loop. Marty and Doc are friends because Marty helped him in the fifties (and in the game, saved him in the thirties) so Doc knew who he was in the eighties and became friends with him, thus leading to him once again do all of those things.
Omnidisciplinary Scientist: Aside from inventing a time machine with an on-board nuclear reactor, he's also managed to build a working refrigerator (well, it can produce ice, anyway) using 1885 components, and a second time machine that runs solely on steam power (again, using components available around 1885). Also, when he meets Clara and lets slip that he's a scientist, he mentions that he's a student of all sciences.
The Professor: In the original draft, he'd been called "Professor Brown" before it was recommended that he'd be called "Dr. Brown" or "Doc". This new nickname became so iconic that during the filming of The Frighteners years after BTTF, Michael J. Fox kept calling the Judge character "Doc".
Sdrawkcab Name: His first two names. His first name Emmett is "time" pronounced backwards, and his middle name Lathrop is "porhtal", as in "time portal".
Sesquipedalian Loquaciousness: Especially in the animated series. In the DVD commentary, it's lampshaded that Doc will use a bigger word when he could easily use a smaller word, such as calling a dance "A rhythmic ceremonial ritual" even though the word "dance" was clearly written.
Symbol Motif Clothing: He's wearing a shirt decorated with locomotive trains in Part II. The same shirt becomes his bandanna in Part II.
Took a Level in Badass: His first appearance in Part III involves him rescuing Marty from being hung by shooting the rope holding him up, then proceeds to get Buford and his goons to run off.
The Von Trope Family: In Part III Doc explains that his family use to be the "Von Brauns". He goes on to explain his father changed it to Brown because of World War One.
Word of Dante:invoked Bob Gale guesses that Doc was involved with the Manhattan project, but became an outcast and spent the remainder of his life trying to invent something beneficial for humanity. Hence the portable nuclear reactor which he sank his entire fortune into. This would also explain his cynical predictions for the future in 1955 ("Of course! Because of all the fallout from the atomic wars!")
Parental Incest: Has a crush on Marty in the first film - much to his horror. Becomes a major problem.
Playing Gertrude: Lea Thompson is just nine days older than Michael J. Fox. Though it does make perfect sense, as for most of the first film (intended as a one-shot story at the time) she's the same age as Marty.
Played By: Crispin Glover, Jeffrey Weissman
Adorkable: A nerd who is more comfortable watching or writing sci-fi than he is with social interaction and who takes notes on what to say to the girl he likes.
As he introduces himself to Lorraine as her "density", she seems amused by it. This probably would've succeeded if Biff hadn't shown up.
Berserk Button: When Biff pushes Lorraine to the ground, it prompts George to react with violence for probably the first time in his entire life.
Eating Lunch Alone: George sits by himself at the cafeteria during lunch in 1955, writing ideas for his stories.
Flashback with the Other Darrin: It may not be particularly noticeable most of the time due to clever camera work and tech, but the shots with George in Part II that aren't stock footage are played by Jeffrey Weissman.
Playing Gertrude: Glover is actually 3 years younger than Michael J. Fox. (averted with Weissman, who is 3 years older). Justified for the same reason this trope is listed in Lorraine's list.
The Southpaw: An early draft had George discover he could punch very strongly with his left hand. The final film has George's desire to protect Lorraine cause him to unleash his inner strength, but close observers might notice he knocked out Biff by punching him with his left hand.
Took a Level in Badass: Marty basically helps him rise to this point. As soon as Lorraine is shoved to the ground, the fire is lit.
Bitch in Sheep's Clothing: The new "nicer" Biff that appears at the end of the first Back to the Future is pretty much an act given that he returns to being a massive Jerkass when he's an old man (in context, he seems really bitter about how Marty Sr. turned out). It's unknown if he's still this way in Part III, after the timeline's fixed.
The Biff of 1985-A cultivates a philanthropist image in his rise to power.
The Bully: Biff to George, and to Marty, and to Lorraine.
Cannot Tell a Joke: Biff is constantly, err, biffing his attempts at wordplay with lines like "Why don't you make like a tree and get out of here"note It's "leave", you idiot! "Make like a tree, and leave!" You sound like a damn fool when you say it wrong! and "That's as funny as a screen door on a battleship."note "Screen door on a submarine, you dork" Presumably everyone is too afraid of him to correct him. He is berated for this by his older self in the second movie.
Corrupt Corporate Executive: In 1985-A, as the founder of Biffco. He apparently has a head for business, as he's basically a small business owner in the 'fixed' 1985 timeline.
Egopolis: Alternate Hill Valley is a gigantic Shrine to Self. The front of his casino (formely the Clock Tower) is a museum dedicated to Biff's life, with a life-size wax statue and film reel describing his rapid rise to fortune.
In the alternate present, we see a headline describing George's murder; Biff, the actual gunman, crows that the police would never arrest him. The article explains that George was headed for a meeting to protest the environmental policies of Biffco.
I Hate Past Me: "It's LEAVE!! You idiot! 'Make like a tree and leave.' You sound like a damned FOOL when you say it wrong!"
In the Blood: Descended from an outlaw, he's pretty much more of the same. No word about how his son turned out, but his grandson Griff's at least as bad as he ever was if not more. And in the game, it's revealed that his father was a notorious bootlegger.
Jerk Ass: Until George stands up for himself, anyway. And he seems more bitter than jerkass in 2015 - given the opportunity to go back in time, he opts to make himself rich rather than do anything to the McFly family.
Older and Wiser: 2015!Biff. He formulates a surprisingly effective plan to make his past self rich, after listening to Doc talking about the risks of meeting an alternate self, and even figures out how to make the time machine work.
Our Founder: Has a wax statue of himself standing in 1985-A's museum.
Agent Mulder: At the start of the second movie, when she learns that the DeLorean is a time machine, she doesn't question it once (although she does sound pretty freaked out when she asks if they're in 2015).
All Girls Want Bad Boys: In the alternate!1986 in the Telltale game, she's dating an ugly, stupid tool rather than Marty - just because he plays electric guitar in a band (the Marty in the alternate timeline is apparently a grade-A nerd who plays the ukulele rather than guitar). This trope is how the real Marty wins her back, along with showing off his guitar talents.
The Cheerleader: Averted. It's implied in Part II that she may have been a cheerleader in high school (a maroon and white school jacket can be seen in the closet she's hiding in in 2015, with the name "Jennifer" and an emblem consisting of a megaphone over the "HV" letters), but she's the Girl Next Door type, and doesn't seem like an Alpha Bitch or The Ditz as is usually seen in this trope.
Guest Star Party Member: Her most significant role was in the second film. Which involved her running around her future home in a controlled panic. The Bobs have noted that if they'd intended on making a sequel, they would not have had Jennifer go to the future with Marty and Doc as they had no idea what to do with her.
High School Sweethearts: Is this with Marty, and we see that they're married with kids in 2015. But the original timeline isn't very happy, though maybe not to the extent of George and Lorraine in their original timeline - they appear to actually be Happily Married. Lorraine even says that she thinks that she married her son out of pity (and this is to her own granddaughter)! Fortunately, it's heavily implied that her and Marty's future becomes much better/happier after Marty prevents the incident that ruined his life from happening thanks to his Character Development.
In-Series Nickname: Is called "Jen" a couple of times by Marty in Part III and in the game.
The Load: Bob Zemeckis and Bob Gale never had a character development in mind for her, stating that had they planned to make a sequel to the original film, they would not have put "the girl" in the car at the end. Sure enough, less than five minutes into Part II, she's sedated and pretty much spends the rest of the series that way. Her actresses aren't even given top billing in the film credits, even though those who play even smaller roles are.
Locked Out of the Loop: It's quite clear that she has absolutely NO idea what's going on when she climbs into the DeLorean with Marty. Catches up fast, though.
Love at First Sight: With Marty, according to him when explaining that the trope is possible to Doc.
Satellite Love Interest: She appeared very little in the first movie and apparently existed only so that Marty would have someone to spill exposition on in the opening scenes. Robert Zemeckis and Bob Gale tried to write her out of the sequels, but the way they ended the first movie made that difficult; she did get some development in the second and third movies.
The Other Darrin: From Claudia Wells, to Elisabeth Shue, and back again. The opening scene of the second film is actually a painstakingly exact recreation of the end of the first, with the actress as the only difference.
Secret Keeper: She becomes this once Marty tells her about (and shows her whats left of) the Doc's time machine.
Berserk Button: Calling him by his nickname "Mad Dog" has apparently been Buford's for a long time as the moment Marty says it in the Palace Saloon, every single person in the saloon either silently runs away or makes themselves scarce.
Chekhov's Gunman: He's first mentioned in the video playing in Biff's Museum in 1985-A.
Disproportionate Retribution: Originally, he shoots Doc in the back over a matter of 80 dollars, involving a horse that threw a shoe (which Buford shot) and the bottle of whiskey that broke as a result. He also shot a newspaper editor who printed an unfavorable story about him in 1884, which made everyone stop keeping track of his kills.
The Dreaded: Everybody gets apprehensive around him. So much so that the newspapers stopped keeping track of all his kills after he'd shot an editor who printed an unfavorable story about him.
Hair-Trigger Temper: One of the reasons he's nicknamed "Mad Dog", and a major reason why everyone is scared of him.
In the Back: How Buford kills Doc in the original timeline. In a deleted scene, Buford does the same thing to Marshal Strickland when the marshal tries to stop him as he heads into town to duel with Marty.
Identical Grandson: A bit tricky to pin down the usual features of a Tannen through that mustache, but he has 'em.
Jerkass: Well, he's a Tannen. What else would you expect at this point?
Malaproper: "I'll hunt you and shoot you down like a duck." "It's dog, Tannen."
Sister of Gerald Strickland. A Crazy Cat Lady Marty meets in Episode 1. Because Marty interacts with her and young Emmett in 1931 they both fall in love, this little mistake throws the timeline into jeopardy and prevents the events of the movie from ever happening.
All There in the Manual: The novel says that Arthur went to WW1 but was discharged for fraudulent enlistment because he lied about his age before he got the chance to see combat. Arthur returned home without even firing a single shot and became a laughing stock. This event destroyed his self-confidence.
Extreme Doormat: Like George, his future son, but overall, his life is less miserable than George's was.