Welcome to your favourite Sci-Fi show, where the intrepid adventurers are about to explore the Beyond yet again. In this episode, though, the plot isn't exactly saving the day. It's more like saving all the days. We open with a sweeping establishing shot of the Pyramids of Southbank, dinosaurs ridden by Chairman Mao and Marie Antoinette stalking past. Something, perhaps never explained, has caused all moments in time to be perpetually present and somehow all contain the same space, too. Alternatively, your adventurers' journey through the plot is what triggers a Time Crash that results in some kind of chronological collapse. This version is more likely to keep your historical figures and landmarks separate, but even then time isn't going to move, and you're going to be trapped in the entire Universe condensed into a split second.
Either situation might not focus on the science aspect of science fiction too much, and rather than a trapped-in-time situation or frozen timeline mess, everything that the viewer is expected to recognise has been gathered together to be happening at the same time as each other, but time continues moving. This is probably your safer option, as it's a lot less taxing on the mind whilst still being easily recognisable as a result of breaking or screwing up the timeline.
Of course, this happening can also create problems when your main get-out clause is Time Travel. It may have got you into this mess, but it probably can't help get you out, as either the accepted timeline that you've been galavanting through is in another reality and/or your time machine can't break out of the "now". You're going to have to find a way to reverse what you did to cause it, usually revolving around people meeting that never should, oddly enough, or a massive frickin' space war. There may also be a timer set as to how long you have to fix time before it completely implodes and, well, not to worry about because then nothing will have ever existed.
It's generally accepted that if this happens then you've really messed up. In fact, it might be used in the story as the default way to show The Biggest Time Travel Screw Up Yet, because just putting Hitler in charge wasn't enough of a consequence for your reckless time-hoppers.
Sub-Trope of Time Crash, your all-purpose shop for different ways to affect history (a.k.a. the catalogue of negative time travel effects), this being one of the potential outcomes of bruising up time a bit. Compare Merged Reality and When Dimensions Collide.
See also: Time Stands Still, when everything effectively freezes in place but for a select few usually the heroes time keeps moving. If you're one of the people who appear to have frozen, it may well be that you experience all of time at once: it may be explained as a massive effect version of localized time dilation in which you are experiencing time at a natural pace, but it's comparatively so slowly that you appear frozen, whilst you can see non-frozen peoples' entire lifespans pass in a second. Place Beyond Time, for somewhere that exists outside temporal reality, so it's effectively experiencing none of time at once and may have a viewing platform so you can look at all of time at once.
- Crisis on Infinite Earths: During the chaos made in the Multiverse there are multiple different Earths fighting to not disappear at the hands of Anti-Monitor. In Earth-1, time is also collapsing, prompting different time periods to happen at the same time but also, it seems, different continuities of different times as there are multiple unthinkable alliances. This is how there are heroes from the present fighting alongside the post-apocalyptic Wild Man Kamandi, the Wild West Anti-Hero Jonah Hex and the World War II soldier Sgt. Rock against the Anti-Monitor's Shadow Demons.
- During Brian Michael Bendis's run on The Avengers, he had Iron Man propose the theory that time is alive in a sense and occurs simultaneously in a nonlinear matter. Then a conflict between Kang and Ultron in a possible future started colliding various time periods and timelines together. Bendis would continue this idea in Age of Ultron, where the idea is presented again by a Tony in a Bad Future who suggests that time travel damages time and enough paradoxes can kill it.
- Child of the Storm has this happen at the end of Book 1, during the climax of the Battle of London, owing to the emergence of Chthon: reality's falling apart, including the distinctions between past and present. Unusually, even after the problem is resolved, side-effects linger, including pre-Industrial levels of forest cover and more than a few examples of Ice Age era wildlife.
- In Diamond and Silver's Excellent Adventure, the repeated use of certain magic damages the fabric of time, to the extent that random portals to various time periods open up, spilling dinosaurs, historical figures, space ships, and other absurdities into the present.
- Discworld: Ankh-Morpork seems to exist in a range of time periods ranging from the medieval (in the early books as a parody of Medieval European Fantasy) to the Victorian (Unseen University working along college rules, the semaphores standing in for the telegraph). The fact that they exist simultaneously (for an example cited In-Universe, a groundbreaking theater called the Dysk and a huge opera house existing in the same lifetime) is explained by the History Monks doing their best to fix history every time there's a Time Crash.
- Timeless: Diego And The Rangers Of The Vastlantic, by Armand Baltazar, is set 20 years (subjectively) after an event like this. It's notable because the Status Quo of time doesn't get restored, and the book portrays the adventures of Diego Ribera, son to a 19th century mother and a late 20th century father, and his adventures through a World Of Adventure where everything from dinosaurs to 22nd century technology has been thrown together.
- Doctor Who: In "The Wedding of River Song", the Doctor goes to meet his apparent death at the hands of the Silence, which is an unavoidable fixed point in time. River Song, whom the Silence had programmed to kill the Doctor, refuses to go through with it, and they end up in an alternate reality where all of time is running simultaneously and beginning to disintegrate. This include details like dinosaurs running around, Charles Dickens on a talk show and Winston Churchill as Holy Roman Emperor who mentions Cleopatra and downloads.
- Legends of Tomorrow: In "Aruba" (season 2 finale spoilers), the Waverider crew have to steal a few things from their recent-past selves in 1916, as the first go-around led to the villains winning and rewriting reality into a Villain World. Rip makes it clear that this is a Godzilla Threshold, as someone carelessly going back on their personal timeline will not only cause them to be erased from existence once the timeline changes, but also risks time folding in on itself. They try to sneak around their past selves to get what they need, but ultimately get caught and have to explain what's going on. During the climax, all of the remaining future Legends, save for Sara, get killed holding off the villains, but are ultimately successful in preventing the Bad Future, and she fades away soon afterwards. That's seemingly the end of it, but once the Present!Legends go back into the time stream, a Time Crash hits and they end up crashing into 2017 L.A., surrounded by futuristic buildings and dinosaurs.
- Star Trek: Voyager: In "The Killing Game", the Hirogen have captured the ship, but instead of killing the crew, they discover the Holodeck technology. They used it to replay all the violent events in the recorded history of the Starfleet database; the crew had their memories altered so they actually thought they were holodeck characters. The Hirogen hunt them, send them to sickbay, and then return them to the simulations (the security protocols were disabled on purpose). The aliens also force Kim, the only crewmember with his memory intact, to keep adding holodeck projectors all across the ship. And then, all hell breaks loose when Seven of Nine and Janeway get their real minds restored, and the holodeck limits are broken: The Killing Game pt. 2 has Nazis and allies from World War II (some of the crew members with their minds still clouded, others mere NPCs) fighting all across the futuristic Voyager ship, that they consider a Nazi stronghold.
- In BIONICLE, this is what is said to happen if the Kanohi Vahi, Mask of Time, is shattered. Vakama gets an epic Staring Down Cthulhu moment when he gets Big Bad Makuta Teridax to back down and agree to his terms, otherwise he would be willing to cause this to stop Teridax from creating and ruling over a Crapsack World.
- The setting of A Valley Without Wind is the result of a Time Crash of unknown origins; the vast majority of people did not survive, and those who did find themselves in a hellish Patchwork World of time periods, most of them haunted with a wind that flays the very soul from the body.
- Noitu Love 2 Devolution: The time period changes in each level because of this.
- At the end of Mr. Peabody & Sherman, the title characters have to fix a rift in the space-time continuum that is dropping historical figures and artifacts into the present day before it ends up at this.
- The concept of "simultaneous time" (which is an oxymoron) or of "time being an illusion" where as far as a person's consciousness is concerned, there is no real "past" or "future", there is only the eternal "Now", for one's current incarnation as well as "reincarnational" selves.
- According to general relativity, this is what would happen if you somehow reached a black hole's event horizon alive: at that point, due to gravitational time dilation, your time relative to the inertial observer frame would slow down to a full stop, and conversely, from your perspective, the "outside" time would speed up infinitely, so all of it would pass in a infinitesimal moment of your own time. Accidentally, it would also mean that in that moment, you would be instantly fried by the infinitely blue-shifted and thus insanely energetic cosmic radiation, as basically all electromagnetic energy the universe will have ever released hits you all at once.
- There is the often considered theory that all of a person's life as they view it is actually in a zoom of memories they experience as that part of the brain shuts down during death, making all of time that they knew taking up a nanosecond of "real time". (Interestingly it incorporates the phenomena of déjà vu and déjà vécu, which in this theory are suggested as people remembering things out of order.)