In a word, clocks.
Yes, you heard us right. Clocks. And not just your garden variety Spinning Clock Hands either. No, this is something entirely different. For some reason, the "space" you travel through when traveling through time looks like a surrealist dimension filled with giant, floating, semi-transparent clocks that Fade In, drift vaguely towards the camera and then Fade Out again, ticking loudly all the while, only to be replaced by another, visibly different clock, all hovering upon a celestial backdrop resembling a starfield, hyperspace, or in extreme cases, the Acid-Trip Dimension. This sequence rarely lasts more than about a minute, and can often resemble a faster-paced, more clock-oriented version of the opening sequence from The Twilight Zone (1959). Less serious works will often include an obligatory cuckoo clock and/or kit-cat klock.
Much more rarely, an Exploding Calendar may appear as well.
It is extremely rare for the characters to notice or comment on the clocks, and it usually isn't specified whether these clocks actually physically exist in the setting, or if they're just an elaborate form of Painting the Medium (though the latter is usually assumed). When the clocks are commented on, it's only for the purpose of Lampshade Hanging, and the hows and whys of the their collective existence are never addressed.
A bit of a Dead Horse Trope nowadays as it's considered too "goofy" for serious time travel stories, although it still shows up a fair amount in children's cartoons.
Examples:
- Dairy Queen Lips: Well, one clock appears, anyway, when the Lips travel back in time to the Stone Age.
- Doraemon: Nobita's desk drawer is linked through some kind of hyperspace that, with a special vessel, you can use to travel through time. Said hyperspace has a lot of distorted clocks flying around.
- Floating clocks appear in episode 12b of Jewelpet: Magical Change when everyone uses Titana's Jewelwatch to time-travel.
- The Black Moon arc of Sailor Moon R, which is based around time travel, does not feature this in-story, but the opening shows the main characters on an otherwise featuresless field on floating clocks and swinging pendulums.
- Superbook: The time travel back to biblical times had some clocks in it.
- Happy Heroes: In the Season 9 intro, the heroes travel through a time vortex filled with floating clocks.
- In episode 4 of Pleasant Goat Fun Class: The Earth Carnival, floating clocks appear in the background when Miss Earth uses her wand to take everyone to the prehistoric age.
- In pre-Crisis Superman or Superboy stories, whenever Clark time-traveled, the years he passed would occasionally be shown in the background of the timestream. Occasionally the Exploding Calendar variant would appear (calendar pages with the year on them), either in the background or being "torn through" by the Boy of Steel/Man of Steel. 1970's "Superboy" #164 used Floating Clocks, as he only was going back in time to earlier in the day.
- The Time Machine (1960) uses this as part of the opening credits.
- A variation on this trope occurs in some adaptations of Alice's Adventures in Wonderland, wherein Alice's fall into the rabbit hole is depicted with floating clocks everywhere — in these cases, she's not really traveling through time so much as she's traveling to another world.
- Doctor Who: The Title Sequence for the Twelfth Doctor features an interesting variation, with the TARDIS depicted as traveling through a dimension that isn't exactly filled with clocks so much as it is itself a clock, and an infinitely spiralling non-euclidean one at that.
- In Day of the Tentacle, when our heroes pass through the time tunnel a couple of items float on by, amongst them, a ticking clock.
- In The Legend of Zelda: Majora's Mask, the cutscene that follows the Song of Time, signifying the player's return to the beginning of the "Groundhog Day" Loop, shows Link falling down a spiral of the game's idiosyncratic spinning clock faces in a white void, as his disposable items fly away from him. Similar cutscenes, showing circles of clock faces surrounding Link, accompany the game's other time-manipulating songs.
- Touhou Project: Sakuya can temporarily freeze time, usually seen in animated works as clocks appearing and fading all over the screen.
- In El Goonish Shive, during the "Parable" storyline, uses of Susan's slow time spell become associated with a background full of clocks.
- The Back to the Future episode "Einstein's Adventure" has a pair of crooks steal the DeLorean as a getaway car after a robbing, and accidentally travel to 1790, Sydney, Australia. When that happens, this is what they see for a few seconds through the windshield.
- In an episode of The Grim Adventures of Billy & Mandy, Grim takes Mandy back in time to stop himself from changing Billy's grade floating in the time stream passing a lot of clocks and watches.
- Parodied in Futurama episode "Roswell That Ends Well" when the ship literally fills up with clocks after falling through a time vortex.
- Lampshaded and Justified in Milo Murphy's Law. The timestream has lots of clocks, which Dakota says was probably someone's idea of a joke. Later on, he ends up causing those clocks to be there in the first place by hitting a living pistachio with a bag of clocks from a dystopian future where said living pistachio plants overthrew humanity.
- Phineas and Ferb have used the clocks and calendar pages variations in different episodes.
- Happens in the The Simpsons "Treehouse of Horror V" story "Time and Punishment", where Homer accidentally travels to prehistoric times with a malfunctioning toaster.
