We Interrupt This Program

Our hero is plonked in front of his or her favourite show when the show is suddenly interrupted, whether by inside or outside forces, to deliver a (usually) shocking and/or plot-relevant announcement.

See also This Just In (where a news program interrupts itself for this purpose) and Extra! Extra! Read All About It! (where a newspaper stops the presses to update the front page with breaking news). See Emergency Broadcast for automated systems which interrupt radio/TV broadcasts or sound alarms on weather radios and mobile telephones.

Examples of We Interrupt This Program include:

Live Action TV

In The Young Ones, a BBC radio broadcast gets interrupted to deliver the guys some vitally important news. Naturally, they don't notice.
In Mission: Impossible, in the episode "Ultimatum," this trope was Invoked by the IMF in conjunction with Coincidental Broadcast. The target of the sting was not genre-savvy enough to question the coincidence that his music program would be repeatedly interrupted with information directly relevant to his own situation.
Used in Saturday Night Live in skits where their version of the founder of Wikileaks statics out someone else's broadcast to send his message.
Before The Cape was released, radio ads for it were released which started with music and interrupted it with a fake news broadcast in this fashion.
Svengoolie's show starts with an announcement: "Calling all stations! Clear the airlanes, clear all airlanes for the big broadcast!"
Monty Python's Flying Circus did this as a gag in one episode where a regular program is interrupted with "We interrupt this program to annoy you and makes things generally irritating for you." and later with "Good evening. We interrupt this program again ,A, to irritate you and B, to provide work for one of our announcers." which then is followed by a a very nervous new announcer doing his job, get a pep talk from his colleagues and having a congratulatory cocktail afterward.

Music

Doctor Steel's song, "Greedy", starts out with a news bulletin about three escaped prisoners of an insane asylum (one of them, we gather, is Dr. Steel).
The 1956 comedy mash-up "The Flying Saucer" by Buchanan and Goodman does this twice. The beginning of the first side of the original 45 ("Part 1" for us in the digital age) pretends to be a vintage rock'n'roll record, which is interrupted by an announcer with the news that a flying saucer has appeared in the skies "downtown". Side/Part Two starts with music again, which the announcer interrupts to inform us "We are not going to interrupt this record," before returning to the music. After a few more seconds he interrupts again with "Yes, we are," and launches into the remainder of the record.

Radio

The infamous 1938 War of the Worlds radioplay begins with a weather report, then a music show featuring "Ramon Raquello and His Orchestra", and transitioned to the news bulletins that started the main story in this fashion.

Videogames

The first episode of They Hunger had the radio station interrupt to inform about "unknown atmospheric phenomena". As the player learns, it turns out to be lightning that creates (some) of the zombies of the game, when it strikes the graveyard at the nearby church.
In Liberal Crime Squad, you can liberally sneak into the conservative AM Radio Station or Cable News Studio, and liberally discuss a randomly chosen conservative issue, liberally helping it getting more liberal. You can also do the same by liberally gunning your way through the conservative security.

Web Original

The short film Batman: Dead End starts with this sort of a news broadcast about the escaped Joker.
The Strong Bad Email "senior prom" from Homestar Runner begins with this. "Let the King have some!"
- "The King of Town's Very Own, Quite Popular Cartoon Show" eventually became an actual episode. "For reals this time!"

Western Animation

In Courage the Cowardly Dog, the intro starts as one of these.
MAD has this as a Couch Gag.
Tiny Toon Adventures had a short where Buster's video game was interrupted for a announcement.

Real Life

In series 38, episode 7 of Have I Got News for You, a crew member walked up to Ian Hislop and whispered in his ear. Ian then announced that cabinet minister James Purnell had just resigned, just as the panel were discussing the various cabinet resignations that has occurred during that week.
The live broadcast of Quatermass 2005 had an on-screen graphic displayed twice, advising viewers that a major news story (the death of Pope John Paul II) was being covered on BBC News 24.
This also happens whenever Royals die in the UK; Normal programming is either interrupted by the picture of the Union Jack and sombre music, or a message telling viewers to change to a news channel. Such events are also likely to disrupt regular programming for the rest of the day. Although it wasn't expected, a good example of both this trope and This Just In is how British Channels responded to the death of Princess Diana.
- Which is very annoying because after the first hour they had absolutely no new news whatsoever, and because every single other channel was telling you to turn to the news channels, you couldn't escape.
Obviously happened on September 11, 2001. You can find plenty of footage on YouTube and it's especially eerie to see how "normally" the day started. Some regular programs took days to come back on the air.
"Turnabout Intruder", the last episode of Star Trek: The Original Series, was pre-empted by the death of Dwight D. Eisenhower. It didn't air until two months later.