Double Take

Erika: (translating for Largo) She likes your cell phone.
Meimi: <Yuki's was eaten by her pet zombie zilla.>

Erika: Yuki's was eaten by her pet "zombie zilla". <Wait, her what?>

"Takes" or Reaction Shots are a staple, in live action and animation.

The Double Take is when the actor glances at something or someone without much emotion and turns away, then, in a moment of realization, snaps the head around with a big expression. Sometimes this can be done as a Triple Take, but take it much further and you move into the realm of parody.

Bonus points if you include an Eye Take, Spit Take, GASP, or if the words which prompt the Double Take are, before the take, unthinkingly repeated by the Double-Taker (as in the example above).

Examples of Double Take include:

Anime and Manga

In an early episode of Gundam Seed, Lacus is being transferred from the Archangel over to ZAFT. In order to fit into the spacesuit, she had to remove her bulky skirt, which she then stores inside the suit, making her look pregnant. When she's handed over to the ZAFT soldier (who just so happens to be her fiancé Athrun), he does a visible Double Take at the sight of her "belly".
In episode 8 of the first season of Sekirei, Minato feels at ease after having a private talk with Tsukiumi about her not losing a fight, which he had with Musubi in an earlier episode. He then wonders out loud if they're not the same despite their differences. He opens the door slightly, and sees Musubi standing by the door. He nonchalantly closes it for a few moments, then opens it again, and after she says something to him, he screams, wondering if Musubi just heard what he said comparing the two girls.

Film

Even robots can fall victim to the double-take: see WALL-E.
In The Tigger Movie, this is Tigger's reaction to Roo asking him to teach the Whoopty-Dooper-Loopty-Looper-Alley-Ooper Bounce:

Tigger: Asa-bwah-ja... WHAT?

Jack Skellington in The Nightmare Before Christmas does this when the paper snowflake he was trying to make ends up, against all laws of symmetry, looking like a spider. That's right, even the laws of symmetry thinks Jack sucks at Christmas.
Done quite a few times in Pinocchio. Examples:

"Honest John": (noticing Pinocchio skipping by) Look Giddy, a little wooden boy, yes... a little wooden boy?!
Gepetto: Who's there?
Pinocchio: It's me.
Gepetto: Oh it's me... "me!?"

The Adventures of Tom Thumb and Thumbelina

Daniel: What do ya see, Godfrey? What do ya see?
Godfrey: The usual, Daniel, the usual. The usual insects, amphibians, indigenous plant life, raccoon guano, tiny girl floating in a sardine can.
(both nod and retreat into the hole; Beat; both return)
Godfrey & Daniel: Tiny girl floating in a sardine can?!

In Disney's |Hercules, while Meg and Herc start talking and falling for one another in a garden, Meg backs up into something pointed (which turns out to be a statue of Cupid, the point being his arrow). Cue a subtle, but definite double take from Meg.
In the film version of The Lord of the Rings: The Two Towers Pippin does one of these when he realizes that the tree he is climbing is, in fact, sentient.
The French soldier in Monty Python and the Holy Grail does a big double-take when he sees the huge "Trojan rabbit" being wheeled up to the gate.
In Monty Python's Life of Brian, after Brian falls into a passing spaceship, the two aliens inside do a double-take at the sight of him. More exactly, their eyestalks do a double-take.
A rather (in)famous one in the James Bond movie Moonraker, with a Venetian pigeon doing a Double Take at Bond passing by in a gondola-hovercraft.
- Another in You Only Live Twice when Osato sees Bond in the SPECTRE control room.
Alan gets one in The Hangover when he's peeing, sees a tiger in the bathroom, continues to urinate, then turns at the tiger again in utter horror and panic.
Teenage Mutant Ninja Turtles II: The Secret of the Ooze features not a double take, but a triple take when Keno notices the Turtles running up behind him.
In Return of the Jedi, when Han Solo instructs C-3PO what to say to the Ewoks, and keeps pulling him back for new orders, finishing with "Hurry up, will ya? Haven't got all day!" the droid responds with a double take.
As the French king of physical comedy, Louis de Funès' Double Takes were nothing short of epic.
- A good one in Delusions of Grandeur, when Don Saluste guides the king of Spain to the bedroom where they expect to surprise the queen with her lover... only to find her old gouvernante, Doña Juana, in the arms of Blaze the valet. Saluste double-takes, closes the door hastily and starts speaking gibberish out of shock.
The Three Stooges, fairly constantly.

Literature

Unseen Academicals has several of these, usually from Glenda, who gets very involved in her thoughts before reacting.

Live-Action TV

Chuck gives us this gem in its very first episode.
In an episode of Father Ted, Bishop Brennan is coming to stay and he is terrified of rabbits. Ted comes down in the morning and the lounge is bizarrely full of rabbits. He sits down and starts to read the newspaper for a while, before finally noticing, leaping up and screaming his head off. A similar thing happens when he completely destroys a car donated as a raffle prize by the diocese in the process of trying to tap out a tiny dent. In the appropriately-titled episode "Kicking Bishop Brennan Up The Arse" he also doesn't realise that Ted has just kicked him up the arse until he's in Rome at an audience with the Pope, at which point it dawns on him and he goes running out.
Buffy the Vampire Slayer. When Vampire!Willow (a second Willow, from an alternate dimension) is spotted by Angel...

Angel: Buffy, I...I just... something's happened that... Willow's dead. (sees Normal!Willow next to Buffy, waving) Hey, Willow. (very confused) Wait a second...
Xander: We're all right there with you.

- This wasn't the first time he'd do this. Just turned evil, Angelus sides with the psychotic Drusilia and The Judge, who's meant to be invincible. That was before Buffy has something stolen for her, a rocket launcher. When Angelus sees it he just knows that it's time to get out of there, and we get a second close up Double Take of fear in case it was missed in the first wide shot.
In the House episode "Alone", Wilson kidnaps House's guitar to force him into hiring a new team. He leaves a ransom note made of letters cut from a newspaper taped to House's wall. When House sees this, he barges into Wilson's office to reclaim his guitar. Wilson smugly proclaims his innocence, then signals the conversation is over by opening his newspaper... the paper with all the bits cut out, causing House to do a (hilarious) double take.
Dollhouse gives us this:

Zone: Who doesn't want to spend some quality time with these awesomely normal people?
Mag: I don't know, it could be all right. The little Asian is kind of cute.
Zone: She's a tech-head. Mag. ... She's a girl, Mag!

While it may have happened at some point in Star Trek (with five different shows and nearly a dozen movies, you check them all to see one), there was definitely one from its creator, Gene Roddenberry. He married Majel Barrett, who had been removed from her role as Number One due to Executive Meddling (this was just after "The Cage" had been shot). Barrett, in order to get back on the show (albeit in a different role) dyed her hair, and was talking to a producer or someone when Roddenberry walked through, said hi, began walking out, and double-took.
In one "Superheroes" skit on Whose Line Is It Anyway, Ryan was Double-Take Boy.
One of Harry Enfield's sketch shows featured recurring characters "The Double-Take Brothers", a pair of gormless unobservant idiots who react this way to everything.
Doctor Who
- "Time Crash/Last of the Time Lords". A huge ship has just crashed through the TARDIS, knocking the Doctor off his feet. He says, "What?", then takes another look and goes, "What?!", and when he sees the name of the ship (SS Titanic), he has to look at it twice before saying "What."
- For the eleventh Doctor, during the episode "The Pandorica Opens" the Doctor is talking with Rory, who was erased from existence a couple episodes ago, about missing something important. He walks away before coming back with the following:

Doctor: Rory, I'm not trying to be rude, but... you died.

In the Supernatural episode "Hammer of the Gods," the brothers are in a creepy (4 star) hotel, and Dean walks around with his EMF detector, trying to pinpoint their Monster of the Week. As he walks down the hallway, he passes an open door, with an elephant in the room. He takes two more steps, looks up from his EMF detector, takes two steps back, and the elephant is gone, replaced by a fat black man. Dean walks away, extremely nonplussed.
Friends
- In the last episode, Chandler and Monica make their way back home to their old, soon-to-be-vacated apartment, where the rest of the gang is waiting to see their kid. Monica shows up with one of the babies, then Chandler enters the scene with the other. Cue massive Double Take from everyone; especially egregious with Joey.
- Joey has a lot of these over the course of the show. When Chandler and Joey have won the girls' apartment from them, they stop by to give them a consolation gift and walk in...to find all their stuff back where it was before, because the girls switched everything while they were out. Chandler stands shocked in the doorway, while Joey strolls in, gets a beer and sits down... and then realizes.
In an episode of Fawlty Towers, Basil does this. He's in the lobby as per usual, when the Major casually walks past him carrying an enormous shotgun. Made even funnier by the fact that he's got it to kill 'Basil'.
In the first series of Blackadder, when Edmund sees the ghost of Richard III.
In Sister, Sister, Tia is being told off for causing the star player of High School to become dangerously close to flunking due to her tutoring skills. Tia denies that she was doing it, and also denies ever tutoring him. However, mid-sentence, she realizes... cue double take, Tamera apparently disappearing when she was present beforehand, and then a cutaway to the outside of the school with Tia's voice screaming "TAMERA!" at the top of her lungs and in a long manner.

Recorded and Stand Up Comedy

In one of Dane Cook's skits he tells he did a a twelve-take, when he saw under his dad's robe when the dad was not wearing any underwear.

Theatre

In On the Town, Lucy does a Double Take between the following lines and exiting the scene:

Chip: Well, goodbye, Miss Schmeeler.
Lucy: Goodbye, Mr. Chips.

Mortimer does a big one in Arsenic and Old Lace after discovering there's a dead body in the window-seat.

Video Games

In Dissidia 012 Duodecim, Kefka does a (fittingly) hilarious one upon realizing that Vaan had taken Terra with him.

Vaan: We'll finish this next time! For now, I'm just gonna take the girl! Catch ya later!
Kefka: (waving) Yeah, it's been a pleasure! Wait, you're, you, you're you w-w... WHAT!?
(beat)

Web Animation

Tucker does this in Red vs. Blue Season 4, when confronted with Crunchbite for the first time.
Seen in this satirical animated short (from 6:40 to 7:42) of Command & Conquer: Tiberian Dawn when a Tiberium Harvester from one side returns to its home base by making a calm, friendly drive past its adversary's base without getting shot at. The base's guards get carried away, only to realize that they've just let an enemy Harvester escape under their noses.

GDI Base Guard: Fuck! Fuck! Fuck! Fuck!

- It's a jibe at the game's Artificial Stupidity: the program's pathfinding tendencies to lead one's units through the shortest route possible, even if it isn't the safest way around. It's lampshaded by the Commando that ordered the Harvester to come home and the Harvester's seemingly Simpleton Voice.

Nod Commando: Harvester Number Two! I want the resources back to the base a.s.a.p.! And don't take a goddamn shortcut!

Web Original

In Dr. Horrible's Sing-Along Blog, Captain Hammer gives Penny one when he realizes that the girl he just "saved" is kinda cute.
One literal trailer for the fourth Twilight film: "Edward looks shocked, and Bella looks stunned/ Twilight, Breaking Dawn... Part 1?" It then cuts to the person literalising, who can't quite believe what he just read, then does a Curse Cut Short.

Western Animation

In the Tom and Jerry short Tom's Photo Finish, Jerry shows a sleeping Tom an incriminating photo. Tom goes back to sleep, then does a Wild Take with his head detaching from his body and crossing to the other end of the Cinemascope screen...
SpongeBob SquarePants: Step Four for the patended SpongeBob SquarePants Bubble-Blowing Technique: Double Take 3 Times.
One Garfield and Friends episode actually shows it during their special episode describing some of the cartoon clichés.
Avatar: The Last Airbender. Aang does a big one at the end of episode 12, Book 2, when he reaches the top of the Ba Sing Se wall and sees for the first time the Fire Nation's Giant Drill.
CatDog. When Cliff and Lube find out Shriek is a girl, they QUADRUPLE TAKE.
Occurs about once per Rankin Bass Christmas Special.
The Twisted Tales of Felix the Cat, after Felix is bummed out that everyone has a magic bag like him:

Roscoe: (flying through the air, hand stuck in out-of-control magic bag) Hi, Felix.
Felix: Hi, Roscoe. (aside) Even Roscoe. (realizes what just happened)

Real Life

In a somewhat funny example, the US Department of Defense's exercise codeword for Defcon 4 is DOUBLE TAKE. Appropriate as Defcon 4 pretty much means "huh, what?" in terms of readiness.