Left It In

This is when someone says "We'll edit that part out later" but then...doesn't. Instead, the whole preceding sequence is included anyway, often for comedic effect. This can be done to make someone look silly or dumb, for irony, or just for laughs. A common variant is when a person is on camera but isn't aware that they're being filmed live, so when they mess something up they'll stop awkwardly and ask for a redo. Or they'll say "you'll cut that out, right?" (The gag can be played up by the cameraman/editor assuring them that, yes, of course it'll be cut out...). Though mostly for comedic value, in rare cases it might be used in a serious manner specifically to make someone look bad or dishonest.

When used in a fictional setting, it almost always requires an In-Universe Camera. Happens often in Mockumentaries and Show Within a Show situations, but isn't strictly limited to those. Can also be used as a gag in Real Life productions, such as plays, broadcasts, or comedy shows.

Compare Fix It in Post, which is Real Life Script Speak uttered during production of a work; you usually won't know about the sequence because it's actually been edited out.

Contrast Throw It In, when a Real Life unscripted performance is included in a production. Left It In is an In-Universe example of someone requesting or mentioning that the very scene they're in should be cut (and then it's not). See also Hilarious Outtakes and Bloopers.

Examples of Left It In include:

Film

In National Lampoon's Vacation, before the family left for their trip to Europe from winning a game show, Clark videotapes Ellen while she's taking a shower, who then tells him to delete it after he's finished. When the family got their camera stolen by a thief while they were in France and they arrive in Rome, Ellen then discovers that Clark did not delete the video of her in the shower at all, when she sees a poster advertising a movie that starred her. Apparently, the thief discovered the video after he stole the camera and advertised it as a movie.
Dr. Strangelove: This is how Stanley Kubrick managed to convince George C. Scott to be so over-the-top in his role as General Turgidson. Kubrick would encourage him to do "warmup" takes in preparation for the real thing. The over-the-top takes thus were used in the actual movie, and hilarity was held by all, except Scott. Scott then swore to never work with Kubrick again, even though he admired the sneaky genius of it.

Literature

A Dubya-parodying character in one of the Ciaphas Cain novels ends an atrociously bad speech with something like "You'll edit that out anyway... what do you mean it was live?"

Live-Action TV

This is a common bit on talk shows:
- Often used by Conan O'Brien in his prerecorded bits.
- Frequently used by David Letterman. He says "we'll edit that out later" but they never do.
- Both Steven Colbert and Jon Stewart do this frequently on their shows. It's always intentionally Played for Laughs.
On Dirty Jobs Mike or his host will occasionally screw up on camera, then Mike will use this line.
- No surprise, as it fits very much with the meta-theme of the show; oftentimes they'll include shots of the crew setting up the very shot you see next.
- In several cases, a job would go bad due to a production accident or the host being difficult. Instead of cutting the whole thing they'll broadcast it anyway.
In The Comic Strip Presents: More Bad News, Vim/Alan breaks the fourth wall and threatens to sue the producers if they leave in a particularly embarrassing item about him. Unfortunately for him he later gets beaten up and left in a coma, so the item stays in.
Often used on Have I Got News for You.
- Double Subverted on one occasion: a panelist asked if a line could be edited out. When told, "No", he sincerely apologised. Paul Merton instantly said "Now that bit, we'll edit out."
In one segment of Chappelle's Show, A reporter is investigating a Jedi abuse scandal analogous to the Catholic priest pedophilia scandals. While interviewing a "Jarth Mader", an anonymous victim who wears a helmet and has a respiration problem, Mader puts his head in his hands in tears. The reporter says "Cut" to the cameraman, but mouths the words "keep rolling" since Mader's not looking.
On the Mary Tyler Moore Show, Mary is interviewing a male author with the intention of cutting in a tape of Murray asking the questions later. At the end, the author asks Mary out. The final result that is broadcast shows Murray being asked out by the author.
There's a typical "hold me back" scene in the final episode of Series 5 of Skins. Nick goes to hold back Rich, but misses his arm, and Rich's actor laughs and steps back anyways. It doesn't make sense within the story, since Rich really wants to punch the guy - the editors must have just left it in.
In the Stargate Atlantis episode "Letters from Pegasus", McKay gives a videotaped message to Ford, who's editing a bunch of these messages together to send back to Earth. McKay recorded the message while severely sleep-deprived, so it's full of rambling, back-tracking, and McKay telling Ford to edit out the last thing he just said.
On Third Watch this is averted when Doc paralyzes his patient while being filmed for a show about the city's greatest paramedic.
Shows up frequently on Top Gear, most commonly invoked by James May.

Pro-Wrestling

On the September 2, 2014 episode of Main Event, Layla grabbed on to Rosa Mendes and pulled down her tunks by mistake. Mendes had no clue how serious it was until Alicia Fox and Paige both pointed out, as this clip from Total Divas. Layla even admits that it could've been worse as Fox pointed out the program is a PG-Show. It was edited out, but there one thing... fans had cell-phones that can record video and you can guess where they ended up.

Musicals

In the Stephen Sondheim musical Merrily We Roll Along, the lead character is a songwriter. He's showing off a new song he's working on, and after the line "They're always popping their cork", he mutters, "I'll fix that line". He never gets a chance to, because they get a booking and the show with the song in it goes up too quickly.

Stand-up Comedy

On one of Rowan Atkinson's comedy albums, he suggests putting his 'Madonna' song in to fill up spare time on the album. Angus Deayton asks to hear it. After Atkinson has sung it, Deayton mutters "No way are we including that".
Eddie Izzard: This trope is practically a catchphrase of his, saying "We'll cut that out" usually once per show.
The comedian Mitch Hedberg had a bit on one of his CDs, mentioning the recording of the CD. After a particular joke fell flat, he joked about adding the sound of audience laughter to compensate.

"All right...that joke is going to be good because I'm going to take all the words out and add new words. That joke will be fixed."

On Paul F. Tompkin's comedy album Freak Wharf, on the track "Apologize For Your Dog", he goes off on a random tangent near the end of the track. After the laughter dies down, he remarks "I'll cut that part out later...{laughter}...I can. I can do what I want. I'll cut out this part too, where I talk about cutting it. I don't care."

Video Games

In one mission of a high-level story arc in City of Heroes, the villainous Dr. Aeon addresses the team via video, gloating about how impossible their task is -- and in the process accidentally revealing what they need to do and what weaknesses to exploit. When he realizes what he's done, he shrugs and says, "I won't say that on the next take." One of his minions has to break the bad news to him that they weren't recording, they were broadcasting live.

Web Original

In the podcast Webcomics Weekly, the hosts often go off on various tangents while talking, or they'll have computer issues while recording (a common occurrence). Someone will say that they'll be fixing it afterwards, but they rarely (if ever) do. In fact, it's become a running gag.
The podcast The Skeptics' Guide to the Universe started off very PG, as the host Steven Novella would edit out profanity. The show has gradually gotten more adult thanks in part to this trope. Due to Steve's shift in editing, the blue humor of the Rogues Gallery has been slowly revealed over the years as Steve has left in more and more of the "too bad you're going to edit this out" moments. Steve himself even plays it up, mockingly saying "Oh yeah, I'll totally edit that out" after someone says something stupid/embarrasing.
Phelous seems fond of this.

Hey, why did I record that? Oh well, there's absolutely no chance that I'll edit it into the final video.

Articles on The Agony Booth will sometimes have the writer make a rather perverted comment, followed by a note to themselves to edit it out before posting. "Don't forget now!"
In his Let's Play videos, Slowbeef often speaks of editing out his failures and certain comments by his guest commentators. It rarely happens, unless there are enough failures that it makes the unedited video tedious to watch.
Tobuscus frequently yells at his just off-camera assistant, "Steven", to edit out embarrassing parts of his Lazy Vlogs. The Running Gag is that there is no editing of the vlogs, just as there is no Steven (we think).
Several times on Spoiler Warning, one of the cast as expressed relief that Josh has gotten himself killed again, so that their previous awful jokes or awkward tangents can be edited out without skipping important gameplay scenes. Shamus keeps them in.
Psycomedia - if you put together a lazy editor and a co-host who enjoys making life difficult for him, you get this trope.

Western Animation

On Family Guy, when Brian joins The Bachelorette, he makes some comments about Chevy Chase to the Confession Cam and then asks if they can cut that part out...and then goes on to say even more things about Chevy.
On the South Park episode, "Volcano", while the mayor's speech is being recorded live...

Mayor: "God, please deliver these kids from... oh, waitwaitwait... okay... 3, 2, and 1... God, PLEASE, deliver these kids from..."

The Simpsons episode "Radio Bar", where Bart pretends to (and the later, for real) fall down a well. Kent Brockman attempts to interview Homer on the air...

Homer: Uh, you can edit out that part, right?
Kent: Homer, we're live from coast to coast.

Used in Barbie: A Fairy Secret. Raquelle tries to discuss the best part about the film she and Barbie costarred in, only for Barbie to show up. Unfortunately, they're at a live coverage of the premiere...