Sorry to Interrupt

"Dark Helmet: Did you see anything!?

Colonel Sandurz: No, sir! I didn't see you playing with your dolls again!

Dark Helmet: GOOD!"

- Spaceballs

Irene needs to talk to Alice and Bob. She goes to Bob's room, opens the door and sees Alice and Bob in a compromising position. "Ok," Irene thinks, "just slowly back out of the room and close the door."

This trope is when someone opens a door, sees something unexpected, and does an about face. They may mutter something like, "I'll come back later," "You seem busy," or "Sorry to interrupt." Now what the people in the room are doing may be Not What It Looks Like, and often isn't even sexual at all. The two people may be summoning a ghost, or conversing with their toys. On the other hand, this covers solo acts.

Afterward, outside the door, the interrupter may start ranting, screaming or searching for Brain Bleach.

A common variation is to play the scene from the other side of the door. Albert and Brenda are doing something innocent, and just at the wrong moment, someone opens the door. They're invariably caught when the potential for Not What It Looks Like is at its highest.

Especially embarrassing when the person accidentally interrupting had previously been purposefully sent away. Or in...certain other situations. If shown from the perspective of the couple interrupted, see Interrupted Intimacy.

Examples:

Anime and Manga
""Sorry for the confusion.""
 * From Suzumiya Haruhi: "Wawawa wasuremono... Sorry. Enjoy yourselves!". Thus spoke Taniguchi when he wandered into a classroom and found Kyon and Nagato on the floor together, just as they had finished .)
 * Not to mention the multiple occasions when Kyon stumbles in on Haruhi molesting/changing Mikuru into a costume. Became almost a running gag within the first six episodes.
 * A few Furo Scenes in Ranma ½.
 * In fact, this is how (male) Ranma and Akane first met. She walks in on him, gets a good look, calmly turns around and then frantically searches for something to drown him with.
 * In Mahou Sensei Negima, we have Negi, who is posing as a fifteen year old with the help of a magic pill while having wounds treated by Ako, who is in love with older Negi. As she treats his wounds, Negi, who is naked, faints and falls on top of her. As Ako struggles to get Negi off her, Natsumi opens the door....... only to quickly excuse herself and leave. Awkward.....
 * In the Beach Episode of Mai-HiME, Mai says, "Sorry for interrupting!" to Takeda and Natsuki.
 * In an episode of Saiyuki, Gojyo and Goku are fighting (what else?) over the one bed in the hotel room they all share. The hotel maid who opens the door believes they are, well, not fighting, and is highly embarrassed.
 * Something very much alike the page quote happened in Gundam's third incarnation, ZZ Gundam. First half antagonist Mashima Sero lives to his admiration for haman Khan by talking to the rose she gave him when his first officer entered the room on accident.
 * In Baccano, a member of one of the more sympathetic character's Nakama enters a train with a knife drawn and orders everyone to get down. At the same time two rival factions of mobsters enter with guns and do likewaise. He promply leaves.

""Sorry for inturrepting""
 * In Get Backers, Genji is in the hospital with Himiko keeping him company. Genji is eating some melon and throws one slice straight in, causing him to choke on it. Himiko leans over to make sure he's okay; cue Natsumi coming in to say hi, and immediately assuming she's walking in on a kiss.

Fanfic
""Hello," said Maddox, looking at the man at Vash's back.
 * In the Kingdom Hearts fanfic Other Halves and Other Tales, it's a Running Gag.
 * In a one-shot for The Hearth Series, one of Vash's attempts to arrest Maddox ends with Maddox handcuffed to a lamp post, with his legs wrapped around Vash's head. While they are in this position, Ramon thinks he hears someone calling for him and looks outside.

"Never mind," Ramon said. It did not take long for Vash to hear a front door open and close."

Fanon
"Dib: "Haha! I've got you now, Zi-- [long, awkward pause] You know what? I'm not going to try today.""
 * The first thing I thought of was actually the Invader Zim fan-made Most Horrible Short Ever.

Film
"Leo: Oh my God!
 * In Spaceballs, Colonel Sandurz interrupts Dark Helmet while the latter is playing with his dolls, leading to the page quote.
 * In The Producers, Leo interrupts Max "feeling up the old lady", but Max has to prompt him to fulfill this trope:

Max: You mean "oops," don't you? Just say "oops" and get out!

Leo: Ahahahahahahahaha...

Max: Not "ahahahahahahah!" "Oops"!

Leo: Oops!

[slams the door]"

"Troi: Would you three like to be alone?"
 * Airplane!. When Otto the Autopilot starts deflating, Elaine tries to re-inflate him by blowing into a tube at his waist. Dr. Rumack walks into the cockpit and sees her apparently performing fellatio on Otto, then turns around and walks out with a stunned expression on his face.
 * That's nothing to the look on Otto's face!
 * Does that technically make it "Otto fellatio"?
 * In Cars, Lightning McQueen goes to talk to Doc Hudson and walks in on Sheriff getting a tune up, which, judging from McQueen's reaction, appears to be the car equivalent of a colonoscopy.
 * Independence Day. Somebody walks in on what looks like a pilot proposing to another pilot.
 * In Star Trek First Contact, Picard is admiring the first human-built warp ship and trying to explain to Data how being close to something makes it seem more real.

Literature

 * In the Robert Heinlein novel Have Spacesuit, Will Travel, Kip enters the room and finds Peewee crying. She doesn't notice him, so he sneaks out and then starts to head back while making a lot of noise so she can hear him coming and hide the fact that she was crying.

Live Action TV
"Hannah: I'm going through something of a homophobic phase - not that I have any objection in principle to men slathering each other with lubricants prior to penetration.
 * In Friends, when Joey, on his way to the men's room, sees Ross kissing Chandler's mom. Joey turns and says, "I'll just pee in the street."
 * In another episode, Joey walks into a room, where Ross suddenly accuses him of proposing to Rachel - Joey "realises" that "This isn't the right room!" and quickly escapes.
 * When Monica catches Ross and Rachel kissing (long after they've broken up) she says: "I'm sorry, apparently I've opened the door to the past."
 * Lampshaded in an episode of House, during a sequence in which at least two people (Wilson and Cameron) separately walk in on the title character receiving a vigorous massage of his bum leg by a physicial therapist. Realizing how suggestive it looks, he shouts, "It's not what it looks like!" to both.
 * Another time Cameron and Chase are making out in a janitor's closet. House opens the door suddenly and simply tosses his garbage out before leaving.
 * Used and played with in Believe Nothing when Hannah walks in on the main character receiving a vigourous and suggestive back massage from his dogsbody.

Adonis: Hannah! There are no sexual undertones whatsoever in this scenario! Are there, Albuman?

Albuman: ... oh."


 * In Torchwood Gwen walks in on Jack and Ianto doin' it in the greenhouse. It's followed by a totally unrelated argument between Jack and Gwen, and then Jack drags Ianto back into the room and is seen undressing again.
 * Once in Matlock, Matlock was being hugged by an old flame (I think), and is walked in on by assistants Cliff and Jerri. Jerri looks shocked, while Cliff says "Whoopsiedoodle," and drags Jerri back out the door.
 * In The George Lopez Show, Max catches George and Angie's sister kissing. Angie's sister, having just gotten divorced, wanted some loving and had grabbed George and started making out with him.
 * In the Seinfeld episode "The Kiss Hello," George enters the room just as Kramer kisses Jerry on the lips. He stands in the doorway for a few seconds, then backs out again.

Web Comics

 * Happens in Fanboys, whenever Paul walks in on Lenny and Sylvia in intimate cosplay.
 * Paul needs to learn to knock.
 * Apparently so does Mumbo
 * This College Roomies From Hell page.
 * In Juathuur, Thomil interrupts Bivv and Emojueel.
 * Happens in this Think Before You Think comic, but it's Not What It Looks Like.
 * Sandra in this Sandra and Woo comic.

Web Original
"Disembaudio: "Hey, guys, I made you some snickerdoodleGOOOOOD LORD! WHAT ARE YOU WATCHING?!""
 * Has happened several times to Phase in the Whateley Universe. The first time was walking into his room to find his roomie Bladedancer doing something to a mostly naked Jade Sinclair. (It was acupressure therapy - Bladedancer is a healer.)
 * There's another hilarious incident when Phase figures out a new technique to fend off bullies- he can, by phasing just right, steal clothes off people's bodies and leave them unharmed. A number of his friends- and his girlfriend- walk in just in time to see him in front of an undressed mannequin holding women's underwear.
 * Yet another incident occurs when Phase figures out a way to make everyone back off- after being asked for a favour from a regen called Peril, he decides to set up a scene where Peril verbally abuses him, he seems to snap and phases through Peril, taking Peril's dick with him. To do so without anyone actually getting hurt, Phase gets Bugs to create a model penis. Cue everyone walking in just in time to see Bugs kneeling down next to his very erect penis. Including his girlfriend.
 * During the Rifftrax for Three Hundred Disembaudio walks in during the rape scene:

Western Animation

 * In one episode of Cat Dog where Winslow walks in on Dog with Cat all the way down his throat and then some. He immediately turns around and leaves saying, "Oh, never mind."
 * A variation occurs in Xiaolin Showdown, when Chase Young has his animal slaves shapeshift to their human warrior forms. Cut to Dojo slithering in, carrying a tray of food... and turning around and slithering right back out without missing a beat.
 * In Robot Chicken some random man does this when he enters a public toilet and sees Ted Turner painting himself blue and screaming "CAPTAIN PLANET!".