On network TV, when sporting events run longer than the scheduled time, the following program (usually syndicated) is pre-empted and the game remains on air until it is finished. In other instances, network programming will be delayed until the game ends, such as how CBS always delays the start of 60 Minutes to allow it to be shown in its entirety.
This practice goes back to a 1968 American Football League game between the New York Jets and Oakland Raiders that aired on NBC, now known as the Heidi Game. With the Jets up 32-29, the last 65 seconds of the game were cut off in the eastern United States when the scheduled three-hour timeslot ended and a made-for-TV movie adaptation of Heidi went to air; NBC executives decided to allow the game to finish, but were unable to tell network master control about it because their phone lines were jammed up by viewer calls about the situation. As luck would have it, in that unaired minute the Raiders scored two touchdowns and won the game. NBC was widely criticized for cutting away from the game (flashing the final score showing that the Raiders won in the middle of a rather important scene only served to piss off both audiences), and made a public apology.
Now, since there is considerable blowback from non-sports fans (and sports fans who enjoy other shows) about joining "your regularly scheduled programming" already in progress, many times cutting important parts of a show (on a show such as CSI or NCIS, the majority of the plot will be set up within five minutes), networks will often block out extra time for this, making the remainder a post-game talk show of indeterminate length. That way, if a broadcast goes long, the game will only eat into the time allotted for the post-game, which will often only last to round out the hour, and THEN go into the rest of the TV schedule. Fox became infamous for initially refusing to follow this strategy, leading to the 7 o'clock hour on Sunday nights becoming regarded as a second Death Slot due to that show's high likelihood of being preempted by coverage of NFL games. The shows Futurama, Malcolm in the Middle and King of the Hill most notoriously fell victim to this, with many episodes only being partially broadcast or burned off later in the week, leading to outrage from fans about how they were being Screwed by the Network. The outrage would increase if the preemption was caused not by the initial game but by Fox showing "bonus coverage" of a different game that was running over its scheduled time. Perhaps in response to this, Fox finally began blocking out the 7:00PM timeslot in 2006.
Because of the popularity of 60 Minutes, CBS will usually delay the start of that show until every NFL game to which it has the rights is over, then air it in its entirety, delaying the network's entire primetime schedule accordingly in the Eastern and Central Time Zones.note This infuriates fans of the network's Sunday shows (especially those that use DVRs) as they cannot predict when their favorite show will actually start (especially if CBS switches to another game for "bonus coverage", and that game goes into overtime). In September 2012, CBS decided to just bump up the Eastern and Central primetime lineups a half-hour on game nights (concurrent with the NFL moving its late-afternoon doubleheader games from 4:15 to 4:25 ET, effectively forcing the issue), though the games still leech into the second half-hour and cause delays, to the point that CBS has to maintain an Twitter/app service that sends out delay alerts; sometimes this has the side effect of killing the 10pm show for that night, a fate that befell a new CSI episode which was rescheduled three times in October and November 2014 due to long-running games.
As the quote at the beginning indicates, this is not just an American phenomenon. A variant on this significantly heightened "geek vs. jock" hostility in UK popular culture in the 1990s, due to The BBC's tendency to show imported American SF/fantasy series (such as Buffy the Vampire Slayer and various Star Trek shows) on BBC2 on weekday teatimes and cancel them altogether whenever some big sporting event happened.
On networks devoted to sports programming, there have been cases of sports preempting other sports. A notable example is ESPN's infamous 2007-14 NASCAR coverage, in which college sports was given priority, and race broadcasts were cut short or relocated; one of the most infamous examples was the 2014 Bank of America 500 (the last race aired on ABC before the new television contract with NBC went into effect the next year) had its first 25 laps preempted due to a college football game between TCU and Baylor running late; the race was supposedly relocated to ESPNEWS, where it was also preempted because of a preseason NBA game in Brazil going into overtime; the race was said to be on WatchESPN.com (which it wasn't), and RaceBuddy (a service on NASCAR's website with multiple camera angles) was not provided because the race wasn't on a cable network; the only way anyone could follow the start was through the PRN radio broadcast, or via the NASCAR mobile app. Coverage was joined at a scheduled competition caution on lap 25, at which point an apology was immediately issued by lead broadcaster Allen Bestwick and a recap of the first 25 laps shown. To add insult to injury, several ABC affiliates actually decided the race wasn't important and aired local news instead. NASCAR itself was also unhappy with the move, and apologized to irate fans.
Professional Wrestling has been a frequent victim of this, the first few years of Monday Night Raw saw annual preemptions for the Westminster Dog Show and the U.S. Open (tennis, not golf) for a week in June and two weeks around Labor Day, respectively. WCW Monday Nitro would get pushed back to 11 pm for NBA playoff gamesnote , and even to this day Fox occasionally kicks Smack Down Live over to FS1 in favor of college football or soccer. AEW Dynamite actually lost their time slot on TNT when Warner Brothers Discovery bought the rights to show NHL games, though they simply moved across the hall to TBS with the same 8 pm start time on Wednesday nights.
Although the trope is primarily associated with sporting events, there can be other causes for pre-emptions of this nature, including awards shows (which notoriously overrun) and scheduled political broadcasts such as the State of the Union address. Often networks will address overruns by either pre-empting an entire night's schedule and filling the remaining time with programming such as Barbara Walters' post-Oscars interview specials, or scheduling expendable reruns.