Channing Tatum passed on the movie twice before Jonah Hill convinced him to take the role.

Jonah Hill lost over forty pounds for his role, because he and Channing Tatum were required to do several physically demanding stunts.

Originally, the drama teacher talks about doing cocaine with Whitney Houston's niece. After Houston died, the line was changed to "doing cocaine with Willie Nelson's horse."

When Channing Tatum and Jonah Hill exit the limo and enter the prom, the two guys dressed as ushers standing on both sides are their stand-ins.

When Schmidt and Jenko go undercover as brothers, their last name is McQuaid. In the original 21 Jump Street (1987), Hanson and Penhall would frequently go undercover as the McQuaid brothers.

All original cast members from the 21 Jump Street (1987) television series have cameos in the film, except Richard Grieco and Dustin Nguyen. In one scene, the bad guys watch the original television series on television, and almost every shot shows Nguyen's character. Grieco and Nguyen later cameo in 22 Jump Street (2014).

Emma Stone was considered for the lead female role. She had to drop out due to scheduling conflicts with The Amazing Spider-Man (2012).

While Jenko and Schmidt are being briefed on H.F.S., a video sharing site is on the computer. Two of the related videos in the sidebar were uploaded by users Chanchan and Brielar, references to Channing Tatum and Brie Larson.

Jonah Hill wrote the part of Captain Dickson with Ice Cube in mind.

Throughout the film, as the two main characters return to "The Chapel," they encounter two female officers who tout their own exploits, including busting a prostitution ring and busting a chop shop run out of a high school auto shop. Both of these cases were plots in season one of 21 Jump Street (1987).

At one point, Dave Franco's character says that he does not trust Channing Tatum's character because he looks like he is forty years old. In reality, Tatum is only five years older than Franco.

Channing Tatum's character is named Jenko after Captain Richard Jenco, played by Frederic Forrest on the original 21 Jump Street (1987) television series. Jenco was the original Captain of the squad.

While appearing on the Howard Stern Show, J.K. Simmons revealed that he was considered for Deputy Chief Hardy, but scheduling conflicts prevented him from being cast. Simmons said upon seeing the movie that this role was one of the few he would like to have played for the comedy.

Jennifer Lawrence, Juno Temple, Julianne Hough, and Gemma Ward auditioned for a role.

The understudy for Peter Pan is named French Samuels. Samuel French is the name of the publishing company that manages the rights to the musical "Peter Pan."

One scene includes the song "Straight Outta Compton" by NWA. Ice Cube, who plays Captain Dickson, was a member of N.W.A. Also, at the beginning of the film Jonah Hill is dressed like Slim Shady, with whom Ice Cube has rapped with. In the sequel, 22 Jump Street, during parents weekend Dickson's wife is asked where she is from to which she replies "Straight outta Compton."

Before the end credits, a montage of various images are shown. One image shows a man at a typewriter. This is a reference to the famous Stephen J. Cannell Productions typewriter logo, which was shown at the end of his television productions, including 21 Jump Street (1987).

WILHELM SCREAM: During the car chase, just before the One Percenter leader crashes his motorcycle into the chicken truck.

Jonah Hill and Dave Franco also played high school classmates in Superbad (2007).

Schmidt's first name is Morton and Jenko's is Greg.

Filmed in New Orleans, Louisiana.

The two women who try to seduce and flirt with Jenko, Ms. Griggs (chem teacher) and Lisa (girl in climactic limousine chase) are played by Ellie Kemper and Lindsey Broad, respectively. Both previously starred together in The Office (2005).

The drug Schmidt and Jenko go undercover to look for is abbreviated H.F.S., which stands for Holy F

cking Sh

t. It is also the first phrase the teenager in the YouTube video says when he takes the drug.

WILHELM SCREAM: During the credits, when a character dives through a window.

Seth Rogen and Evan Goldberg did uncredited rewrites on the script.

Two of Dave Franco's movies, 21 Jump Street (2012) and Warm Bodies (2013), feature the same two songs on their respective soundtracks, which are John Waite's "Missing You" and "Midnight City" by M83.

Jonah Hill's character uses a SonyEricsson Xperia Play. This was Sony's abandoned attempt at launching a PlayStation phone. Columbia Pictures is owned by Sony Pictures, so it was expected to see Sony Ericsson mobile phones in the movie.

Cameo - Holly Robinson Peete: appears as an older Judy Hoffs when the guys choose the car from the motor pool.

Spoilers:

The trivia items below may give away important plot points.

Johnny Depp's character, Tom Hanson, eats in every scene where he appears. Hanson ate often in the original 21 Jump Street (1987) television series, sometimes several times during each episode, and did so often in scenes vital to the plot.

Hanson appears in disguise as a biker eating a jar of peanut butter, based on a suggestion by Johnny Depp during his last season on 21 Jump Street (1987). Penhall also appeared in disguise as a biker, based on one character's dress in the original series. Jonah Hill specifically wrote the disguised characters for Depp and Peter DeLuise.

While undercover, Schmidt's cover is almost blown by someone he knows personally, and he avoids this by pushing her away and saying that she tried to grab his private parts. This same thing happened to Johnny Depp's character in Donnie Brasco (1997) while he was undercover. Depp plays Tom Hanson of DEA in this film.

When Jonah Hill and Channing Tatum come across the biker gang in the park, one of the bikers says, "If you guys are cops, then I'm a DEA Agent." This character is later revealed to be a DEA Agent.

At the end of the film, it is revealed that one of the bad guys is actually Tom Hanson, played by Johnny Depp, from the original 21 Jump Street (1987) series. He has been undercover for years with the villains using the alias D.B. Following 21 Jump Street, Johnny Depp played another cop who went undercover long term with criminals: Donnie Brasco (1997).

When Schmidt and Jenko take H.F.S., Jenko remarks that it tastes like Cool Ranch. Soon afterwards, they run into Coach Walters, carrying a bag of Cool Ranch Doritos. It is later revealed that Coach Walters is the mastermind behind H.F.S.

Footage of Dustin Nguyen, from the original show, appears on television screens during the shoot-out at the prom. Whenever Nguyen is shown, a television screen gets shot.

When the two undercover DEA Agents are gunned down, it actually conflicts with the original series episode 21 Jump Street: Back from the Future (1990), which features two elderly, retired officers reminiscing about past cases (Clip show episode).

The first clue that track coach Mr. Walters is the supplier comes shortly after Jenko and Schmidt take HFS at the school. Jenko comments that the drug tastes like Cool Ranch Doritos. In the very next scene, the pair meets Mr. Walters, who is snacking on a bag of Cool Ranch Doritos.

Continuity

Immediately after the fight at the party ends, Schmidt's back has no stab wound. A few shots later, it's revealed he has been stabbed.

When Schmidt and Jenko first open the door for their party, Zack, Roman, and Delroy are on the other side. Zack and Roman walk in, and the door closes. Delroy never walks through the door.

After the gun fight at the hotel, Jenko vomits on Schmidt's white jacket. Later in the next scene, the vomit on the jacket is gone.

When Jenko writes on the board in AP Chemistry after he takes the drugs, he writes with a piece of chalk. When the camera angle changes, the board is a whiteboard, with writing in marker.

Schmidt and Jenko walk through church doors that are covered with old newsprint, which disappears as they enter the church.



Factual errors

The officers' mistake at the beginning is not accurate. A police officer is never required to read a suspect their Miranda rights. Miranda rights only become relevant when a person is in custody and being interrogated by the police. Then even if you are not read your Miranda rights, the only consequence is that the police cannot use anything you say as evidence against you.

Eric received early admission to the University of California at Berkeley. In real life, none of the University of California campuses allow early admission.

Never pull a knife out as it could increase the bleeding (though in this case it looks like it is safely lodged in the shoulder blade and cannot have punctured any major blood vessel).

The process of expelling someone from a public school isn't immediately completed the way it is show in the movie. The decision could be appealed at several levels before it was confirmed. And in many cases, the students would be allowed to remain in school during the appeals process as long as the situation didn't involve any crimes (which didn't apply here, as Jenko and Schmidt were expelled for fighting during a school play).



Incorrectly regarded as goofs

During the limo chase, Jenko mentions covalent bonds in context of lithium batteries and potassium nitrate. A bond involving metals would be ionic, not covalent. However, Jenko might not master the whole concept involved yet, and this is clearly played for laughs.

Firing a gun in the air wildly like Jonah Hill did in the park scene would be grounds for immediate termination in most police divisions. However, this is clearly played for laughs.



Revealing mistakes

During the motorcycle chase, one gang member shoots a gun with his right hand while appearing to accelerate. The throttle control is on the right handlebar.

Much of the Korean writing in the church is grammatically incorrect, the type of translation produced by online translators. For instance, the Korean version of "Aroma of Christ Church" has Christ Church as the possessive of the word aroma, i.e. "Christ Church's Aroma" or "The Aroma that Belongs to Christ Church".

The rear-view mirror has been removed from the Hyundai, the Ford Mustang, the Porsche, and the red Mercedes.

When Jenko is playing with chemicals with his friends blowing stuff up he gets a bit of the chemicals on his hands. When the guys run away from the bomb, Jenko can be seen touching one of the boys arms. Covered in acid, this would clearly cause a reaction.

Obvious double for Tatum in the end credits when his character is having sexual intercourse with the teacher.



Audio/visual unsynchronized

Eric tells Jenko that he doesn't trust him because he looks 40. When he says "After a stunt like that, there is no way you can be cops," his mouth doesn't move.



Plot holes

Jenko does not hear the biker come onto his left before he shoots at him at 1:14'.



Character error

The paramedic does not remove the venous tourniquet he just put on Molly's left arm before leaving her and Schmidt have a chat at 1:40'55".

When Schmidt gets stabbed at the party and Jenko pulls the knife out of him and Molly pours alcohol on the wound and they tape a napkin on the wound. Schmidt would need to get medical attention.

The paramedic did not prepare any material for a venous puncture (used for fitting an intravenous line) before setting a tourniquet on Molly's left arm.