A lot of times in media and in Real Life there's a friend (or a group of friends), a very good friend whom you may have known since you were kids. But there's one small flaw within the friendship. The friend in question always gets you into serious trouble. It's usually stuff like trying to get you to break curfew, violate your parole, drink underage and do drugs. The toxic friend will guilt-trip you for not going along with what they want and accusing you of "changing." They'll say things like "Man, you've changed. You used to be cool!", or "Come on, it'll be fun!" And of course, all of the above will almost certainly lead to serious consequences. This is almost the 2000's variant of The Aggressive Drug Dealer.
More often than not these characters are usually plot devices for the protagonist to get into a horrible situation for the purposes of an Aesop. Under normal circumstances, the protagonist in question is usually a rational thinker when not around these types of friends. But when they hang around them they become ridiculously impressionable and naive and easily misled. The friend could be generally well-intentioned and benevolent, but still not a good friend in the greater scheme of things. Also expect these friends to be from the Wrong Side of the Tracks, while the protagonist usually has a squeaky-clean square background (though not always). If they're malicious, they may try to cut off their new friend from old ones because "They Were Holding You Back." If the friend is female, expect her to be troubledand possibly promiscuous.
The toxic friend could also possibly be a passive-aggressiveEt Tu, Brute? and saboteur, like a crabs-in-a-barrel kind of thing. Can be a comedic trope but more often than not it has darker implications. It's also possible for the Toxic Friend to be a significant other as well. Oh, and expect the Toxic Friend to have a very low mortality rate. In a darker sense, serial killers can be Toxic as well by turning their friends, family, and lovers into accomplices.
Sensei for Scoundrels is this trope applied to the student/mentor relationship. See also Peer Pressure Makes You Evil. May also overlap with Femme Fatale.
See also Poisonous Friend, who is "toxic" in a completely different way than a Toxic Friend, and The Corrupter, who has a different kind of bad influence.
In Death Note, LightYagami is this to his girlfriend Misa; being a psychotic Serial-Killer Killer, he wins her allegiance by killing her parents' murderer and quickly turns her into a cruder, deadlier version of himself. Not that she minds, or that she wasn't more than a little unhinged to begin with.
Amanda from Taken. Enticing her friend to lie to her father, and sleep with French men, because she heard that they are good in bed.
Lifetime Movies tend to love these characters. Almost always female, almost always bitchy, and always ready to cause trouble to the Girl Next Door.
Some people see Juno from The Descent as this. Her intentions may be debatable, but the fact she slept with her friend's husband indisputably put her in this category.
In Brokedown Palace Alice Marano is this to Darlene Davis. Some fans also believe that Alice was the one responsible for the drugs, and that she was a drug smuggler all along.
Evie Zamora from 13 to the highest disturbing degree. Evie introduces Tracy to shoplifting, underage sex, hard drugs, and seducing older men. And the worst part is that she's such a Manipulative Bitch, she makes her mother believe it was Tracy who brought her into this, not the opposite.
In the obscure 1990 romance thriller called A Girl to Kill For. Sue is this to sweet natured yet gullible Chuck. More or less seducing him into situations that kept going From Bad to Worse. Can't help but feel sympathy for the poor guy.
Male example from Save the Last Dance: Malakai to Derek. Derek is one of the few young men in his school who is headed for (and actively seeking) a brighter future, while fresh-from-juvie Malakai seems bound and determined to drag him into the gang scene. Derek, for being a bright guy, gets really stupid where Kai is concerned.
In the film Cherrybomb Malachy's parents view Luke as this. Whether it's justified is open to interpretation.
Megan Stewart is this to sweet wholesome Amy Herman in Megan is Missing. Amy really wanna prove she's not a sheltered little girl to Megan. Of course naturally this leads to disturbing disastrous consequences for both.
Played cartoonishly straight with the thriller/horror film Chaos.
In The World's End, Gary's fixation on the pub crawl certainly gets the 'Five Musketeers' into a lot of trouble, and it's made clear that even in their younger days he wasn't a particularly good friend to them in many ways.
A Goofy Movie has an example of a toxic friend getting a parent in trouble with his kid. Pete gives Goofy parenting advice to help improve his relationship with Max... but since Pete is both overbearing and distant, and has a bad relationship with his own kid, PJ, as a result, the advice does more harm than good.
The "Use Your Decision Process" examples in most American high school Health textbooks are filled with this. A typical example is "Alice has a friend named Bob who she has known since she was a kid. But Bob has been acting erratic and paranoid lately. Alice thinks he is doing drugs but is not sure. What should she do?" or "Bob's girlfriend Alice has been pressuring him to have sex with her. She claims she will break up with him if he doesn't. What should Bob do?"
Enid Nightshade from The Worst Witch books. In chanting she deliberately sings out tune, getting Mildred in trouble for laughing at her. She turns her cat into a monkey which escapes and is blamed on Mildred again. On the sports day she bewitches a pole to shoot up into the air with Mildred on it (she ends up crash landing in Miss Cackle's office). Mildred is threatened with expulsion for this but Enid keeps on going, locking herself and Mildred inside a closet when the other girls are in assembly.
In House the eponymous protagonist is this for Dr. Wilson.
In How I Met Your MotherBarney plays this role to the rest of the main cast, but mostly to Ted, whose corruption he views as a pet project.
Ironically, as the show has progressed, even as Barney rubs off a bit on Ted (mainly by encouraging him to live in the moment and helping him to enjoy life to the fullest), he has really been more influenced by Ted in terms of growing emotionally and romantically (even taking a class taught by Ted on how to be a good boyfriend).
Sam Puckett in iCarly. Although it's more in general mayhem on the show, a 'real' Sam would be dragging Carly and Freddie in a debauched world of drugs, booze, sex and criminal behaviour.
Dave was this to Hurley in the flashbacks in LOST, except for the small detail that he doesn't exist.
Del to Denzil on Only Fools and Horses. When Corrine listed a number of times that Del had screwed him over and conned him into joining one of his failed get-rich-quick schemes, Denzil's simple reply?
Denzil: Yeah I know, but he's a mate!
In some ways, Del Boy is this to his brother Rodney. At one point, Rodney is trying to defend his brother to his wife by saying, "Look, I agree that Del can get a bit out of hand, but I think it's unfair to say that everything he touches goes wrong." At this point the bus behind him promptly explodes due to a faulty radio Del installed over the main fuel line. Some of his more notable exploits have been things like convincing Rodney that he is the 'man of the house,' causing him to break his wife's boss's nose, and convincing Rodney to stay on a trip with him despite the fact that Rodney, 26, will have to pretend he's 14 the entire time he's there.
Faith to Buffy, in season 3, especially in the episode "Bad Girls". She convinces her to skip school (which is something she already did when she needed to fight monsters, but she didn't need to at the time) and steal.
Tony in the first two seasons, then Cook, in Skins.
Georgina is this to Serena in the Gossip Girl series.
Kramer to everyone he encounters in Seinfeld. It's nearly impossible to follow Kramer's advice and not get into trouble, yet people keep listening to him. Kramer, of course, never gets into trouble himself.
On Suits Mike was on his way to becoming a lawyer when his best friend, Trevor, convinced him to sell cheat sheets for an exam. The two end up expelled from college and blacklisted, crushing Mike's dreams of becoming a lawyer. The series kicks off with Trevor convincing Mike to act as a one-time drug courier, with the drop-off being a police sting, which he barely dodged. Both Harvey and Mike's grandmother have warned him to drop Trevor because he's the anchor dragging Mike down. Despite everything, he still was willing to give Trevor more chances... right up until he exposed Mike as having never attended Harvard.
As the series progresses Harvey is becoming this to Mike. He forces Mike to take sides in his dispute with Jessica even though he should realize how dangerous it would be for Mike to oppose the firm's managing partner. When Mike caves in to Jessica's extortion, Harvey treats it as the worst form of betrayal since he seemingly expected Mike to commit a Stupid Sacrifice over a fairly petty matter.
On Community, Leonard and his 'Hipsters' gang have an extremely negative influence on Pierce. Eventually getting him caught by campus security and requiring Jeff to bail him out.
Jeff himself can have a tendency to be this for his friends. They tend to look to him as The Leader, but it's gradually been implied that, while he can talk a good talk, his solutions to the various problems they face can do more harm than good and that he's not someone who should be followed or emulated that closely.
Jeff's former law firm colleague Alan is this to Jeff.
On American Dreams Roxanne sometimes borders on this in her friendship with Meg. Occasionally subverted — although she was normally the "good girl", Meg was quite capable of doing dumb and/or rebellious things all on her own.
Sugar and Kim from Sugar Rush, although to a somewhat lesser degree than is presented in a lot of other fiction.
Lucy to Ethel in I Love Lucy, one of the earliest TV examples. Ethel becomes very Genre Savvy about Lucy's influence on her, but still can't resist Lucy's wheedling to join in on her latest Zany Scheme.
On The Mentalist, Patrick Jane is an absolutely horrible influence on the CBI team he works with. Over the course of the series so far, he's talked them into planting evidence, coercing confessions, entrapping suspects, and profiling. This corrosive influence on their respect for the law they're supposed to enforce (and its potential to endanger their careers) is lampshaded by a By-the-Book Cop in the episode "Black Gold and Red Blood," but as Jane is a Showy Invincible Hero who looks out for his friends, any negative consequences they suffer for going along with him rarely last more than one episode.
In the backstory of Person of Interest Det. Stiles was this to Det Fusco. Stiles helped out Fusco when Fusco was going through a messy divorce and when Fusco wanted to repay the favour, Stiles got him involved in corruption, drug dealing and murder. Fusco is revealed to be a very decent guy but his unwillingness to turn his friends in caused him to become a Dirty Cop.
In Luann, T.J. fulfills this role with Luann's brother Brad. He has gotten Brad into trouble with his borderline illegal schemes and other inappropriate behavior. However, he has done other things that were nice, and it's been implied he has Parental Abandonment issues...doesn't justify the borderline illegal schemes, though.
Already being an experienced fighter, Ta'Darius recognized this was happening between himself and Truth Martini, who he went to in hopes of learning the art of professional wrestling and distanced himself from The House Of Truth once it was agreed he had trained enough with them. Unfortunately, Ta'Darius Thomas still fell prey to the manipulations of Jimmy Jacobs and joined Decade.
Surprisingly enough, it turns out Master Miller played this role for Big Boss, who when they met wasn't quite sure whether he wanted to take on his old friend Zero and the CIA directly and make himself an enemy of the world or create Metal Gears with nukes mounted on top of them. Miller was eventually the one that turned back to the US and supported Solid Snake against Big Boss but it was fair to say he certainly wasn't the influence Big Boss needed when they started working together.
Fallout: New Vegas gives you the opportunity to BE this to your companions if you so choose. Specifically you can convince 2 of your companions to become vengeful killers, and another to stop taking her medications so that she becomes a savage beast randomly attacking anything in sight.
Depending on your point of view, Renegade Shepard in Mass Effect. The best example is Garrus' loyalty mission in 2, where you can totally encourage his vengeful 'I AM THE LAW!' mentality.
Invoked in Pokémon X and Y. To evolve the Fighting-type Pancham (a naughty kid panda) into the Fighting/Dark Pangoro (a panda gangster), you need a Dark type in the party when it grows to level 32.
Vriska from Homestuck. Dealt with realistically, as most of the other characters can't stand her as a result of her acting like this - by the time her story starts, most of her best friends have already dumped her over an incident where she caused one of them to get seriously injured, with even Karkat calling her a backstabbing sociopath.
In Dominic Deegan, Bumper and Stunt are introduced as a pair of thieves, but Bumper quickly proves to be the sweeter and more rational of the pair. This increases until in the Two Thief or Not Two Thief storyline Stunt is pretty much exactly this, going for bigger and more problematic illegalities all the time and dragging his best friend along. Until Bumper can't countenance the stuff they're involved in anymore.
For bonus points, Bumper turns out to be from a good family fallen on hard times.
The Bumper-going-a-sleight-of-hand-show-to-raise-Stunt's-bail-again scene that opens T To NTT is pretty emblematic.
At the end of the Two Thief storyline after nearly getting him and Bumper killed, Stunt realizes that he's been a pretty bad friend to Bumper. When Bumper offers to join him on another adventure, Stunt tells Bumper to stay in Barthis where he's made a decent life for himself for his own good.
In Modern Day Treasure Seekers, Cade's parents felt this way about Sam, but came to accept her. However, the flashback shows her hopping a fence with a sign reading "No Trespassing", with Cade going along with her, implying that she influenced him to get into trouble.
Coyote is written as one of these to Rabbit in this retelling of a Native American myth from Myths Retold.
Patrick in SpongeBob SquarePants. Then again, it's just as often Spongebob with Patrick, or Spongebob with Squidward.
Bart Simpson is often this to Milhouse, to the point that one episode focused on Luann forbidding Milhouse from seeing Bart because he's such a bad influence.
Bart: What's she got against me?
Milhouse: She says you're a bad influence.
Bart: Bad influence my ass! How many times have I told you not to listen to your mother!?
Bart towards Ralph Wiggum, as well, nearly ending in the Mayor's accidental death.
Charlie "Big Time" Bigalow to Terry McGinniss in Batman Beyond. Before Terry became The Atoner and Batman, he was a juvenile delinquent due to Charlie's negative influence. It's because of Charlie that he did time in juvenile hall.
Gorillaz bassist Murdoc was this to singer 2D, who remained oblivious to their Type 1 Vitriolic Best Buds relationship throughout Phase 1, attempted and failed to fight back in Phase 2, and now appears to be realising exactly how toxic Murdoc is to him.
Lamilton Taeshawn in the episode, Smokin With Cigarettes, was this to Riley (as if Riley really needed anymore help). But in the end, Lamilton proved to be too much of a hellion for Riley to handle.
When Family Guy's Brian goes to rehab for his coke problem, his therapist points out that Peter is a horrible influence on Brian.
Peter is pretty much this to anyone to whom he offers aid due to being an idiot.
Bill Clinton ended up being this to Peter.
Dodie Bishop of As Told by Ginger. All her plans revolve around making herself popular and she shows little to no regard for Ginger and Macie unless they are helping her. One memorable example has Dodie convincing Ginger to ask her teacher out on a date.
Likewise Miranda to Courtney, the latter of whom is pretty decent but Miranda does everything she can to keep her from interacting with Ginger. At one point even getting an older cousin to help in a scam.
One has to wonder why Penny Proud even bothers to hang around with Dijon or Lacienaga, given how often they either screw her over, abandon her, or get each other into bad situations.
The shorts on House of Mouse depict Daisy Duck as this to Minnie Mouse.
Chozen has Jamal, Phil's ex from prison. After Jamal gets out, he tries to reconnect with Chozen, and immediately starts screwing up every aspect of his life, to the point where he tries to convince Chozen to become a petty criminal like him.