Janitor Impersonation Infiltration

"Arthax: That was... Demeaning.

Yeagar: I never knew you could storm a castle like this...

Nodwick: The thieves' guild would be unstoppable if they invested in blue overalls with the name "Al" embroidered on them."

- Nodwick

Okay, so you have to break into this high tech science lab, or a government facility, or a fancy bank, or something. It doesn't really matter what this place is to you, because it's swarming with security and there's no way you'll ever get in...or is there?

Enter the Janitor Impersonation Infiltration. Custodians, janitors, cleaning ladies, what do these people have in common? They have access to every room in the building and might as well be part of the scenery. No one pays attention to them or wonders what they are doing sneaking around after hours while everyone else in the building is gone. So if you are looking for an easy-in, they are perfect candidates for impersonating when one has to steal that secret formula or those hidden financial records.

Other similar jobs which have the same relative anonymity of the janitor and are Beneath Notice may also qualify for this trope. Being that these people might be secret agents, there's a definite possibility of Almighty Janitor overlap. Compare Dressing As the Enemy, The Infiltration, Room Disservice and Delivery Guy Infiltration. If the impersonater seems to do this often in different situations it might be a case of Why Do You Keep Changing Jobs??

Anime and Manga

 * Spike from Cowboy Bebop, infiltrates a government facility as a Janitor in Cowboy Bebop The Movie.
 * Textbook example in Darker Than Black when Hei needs to infiltrate a science facility and gets a job as a janitor to do so.
 * In Magical Girl Lyrical Nanoha Strikers, Numbers Cyborg Due disguised herself as  to successfully assassinate  . Having shapeshifting abilities helped.
 * In Mega Man NT Warrior, Ms. Madd infiltrates in this manner so that she and Mr. Match can compete again in the N1 Grand Prix.

Comic Books

 * Chameleon does this in the very first issue of Spider-Man, leaving the real janitor bound and gagged in a closet.
 * Used in an issue of Catwoman when Selina infiltrates a police station. One cop even mentions that the cleaning lady is supposed to have the day off, but doesn't pursue the inconsistency beyond that.
 * Taking a leaf from The Shadow's book (see below), the Batman has also masqueraded as the janitor at police headquarters. Sometimes his disguise amounts to a mop and overalls, a hat and a fake beard over his Batman costume.
 * In Huntress #5 (the 2012 mini-series), Helena disguises herself as a cleaning woman to sneak into the Lion's fortress.
 * Scarlett attempts it in the No Dialogue Episode "Hush Job" in G.I. Joe Yearbook #3. In an attempt to rescue Snake-Eyes, she sneaks into Cobra HQ disguised as cleaning woman, with Snake-Eyes' wolf Timber hidden inside a cannister vacuum cleaning. However, the Cobra sensors pick up the huge amount of weaponry she is carrying and she is exposed.

Film

 * In Zoolander, Derek and Hansel try to steal proof that Mugatu is trying to have Derek assassinate the Malaysian Prime Minister by dressing up as Janitors.
 * They dubbed the character voices onto completely different actors because Derek's makeup skills are just that amazing. (Disguised Derek turns left in this scene. Oops.)
 * In X 2 X Men United, Mystique shapeshifts into a janitor to get in and out of a government facility with information on Magneto's prison guards.
 * She employs Obfuscating Spanish when challenged. "Estoy echando la basura. Garbage."
 * Simon Templar does it in The Saint movie, seeking into the Big Bad's office disguised as a cleaning lady.
 * In Fist Of Fury, Bruce Lee's character, Chen, disguises himself as a telephone repairman to infiltrate the Japanese karate school.
 * The Fugitive (1993). Kimble dresses as a janitor to get into a hospital and use its computer system to locate the One Armed Man.
 * Sneakers. Karl dresses as a gardener to get inside the Playtronics building by pretending to need to use their bathroom.
 * Used twice in Undercover Brother.
 * At the beginning the title character dresses as a janitor (complete with Latex Perfection mask) to infiltrate a bank.
 * The B.R.O.T.H.E.R.H.O.O.D. agents pose as the Island Fortress Cleaning Service to infiltrate The Man's island base.
 * In Machete, Machete shows up at the Big Bad's mansion with gardening tools, and the guards just let him in.
 * Horace and Jasper try this in Disney's One Hundred and One Dalmatians, as electric repairmen. It doesn't fool the nanny, so they just barge their way in.

Literature

 * Common in Discworld. Especially popular with the history monks, one of whom actually is an Almighty Janitor.
 * An especially interesting example in Monstrous Regiment, where Polly's regiment have to "disguise" themselves as washerwomen without revealing they're all really women. They are unconvincing as females.
 * Otherland: Olga Pirovsky infiltrates the tower of the J-Corporation disguised as a cleaning lady.
 * In Harry Potter and The Deathly Hallows, when the Trio infiltrate the Ministry of Magic, Ron disguises himself as Reg Cattermole, a lowly magical janitor.
 * Happens frequently as part of the Zany Schemes in the works of PG Wodehouse. In Something Fresh, the first novel set at Blandings Castle, hero Ashe Marson and heroine Joan Valentine are on opposing missions to steal a prized scarab and disguise themselves as a valet and a ladies' maid, respectively.

Live Action TV

 * The Doctor disguises himself as a cleaning lady while sneaking around the villain's compound in the Doctor Who serial "The Green Death".
 * On Burn Notice Michael decided to pretend to be a weekend janitor so he could steal some high tech access codes. When that only got him so far, he added a drunken Wounded Gazelle Gambit to do the rest.
 * On Saved By the Bell, Screech dresses as a female janitor to get into the girls' locker room.
 * Daisy from Dead Like Me once dressed as a cleaning lady to reap someone in their hotel room.
 * Mr. and Mrs Smith (1996). In the pilot episode Mr. Smith (Scott Bakula) dresses up as a janitor to infiltrate a target installation and acquire information.
 * Human Target: a group of bad guys infiltrate a museum dressed as maintainence staff, with Chance and Ames among them.
 * Chuck has on more than one occasion gotten by security by pretending that someone has called the Nerd Herd to fix a computer problem.
 * In CSI the Miniature Killer.
 * CSI: NY had an episode where Flack dressed as a parks department employee as part of a group setup to catch a suspect.
 * The killer in the Criminal Minds episode "Poison" planned on fatally poisoning everyone at his old workplace, which he snuck into disguised as a maintenance worker.
 * In the Hustle episode "Eye of the Beholder", Ash gets a job on the cleaning crew at the museum so he can scope the place out as part of the team's plan to steal the Crown Jewels.
 * Rain does this in an episode of Naturally Sadie to get proof that a famous designer is stealing Margaret's designs.
 * The Leverage crew does this all the time--usually it's Eliot posing as a janitor, but Hardison and Parker have done it as well.

Radio Drama

 * The Shadow used to maintain a cover identity as Fritz, the janitor at police HQ, that allowed him to snoop about in the police files to his heart's content.

Video Games

 * Prototype: Alex Mercer. Canonically he only does this - literally consuming and assuming the form of a janitor - once, and hates himself for it.
 * One of the missions in Mafia II has you enter a mafia controlled hotel that is having a meeting of the head of a rival family but dressing up as cleaners. They clean up the blood of some unfortunate person while planting bombs.
 * In Nancy Drew: The White Wolf of Icicle Creek, Nancy Drew acts as the lodge's new cook and maid in order to investigate the lodge guests.
 * Roger Wilco in Space Quest III infiltrates Scum Soft by posing as the janitor. Since he really is a janitor, it shouldn't be too hard, but he can still blow it and get killed by security.

Web Comics

 * This What's New With Phil and Dixie strip from Dragon Magazine #63 has a guy dressed as a cleaning woman sneaking into a computer lab.

Western Animation

 * Kim Possible had an episode with a government agent mentor who turned up as the janitor. Kim didn't want anything to do with him because she thought he was just the janitor.
 * Centurions had an episode where the main villain had infiltrated the installation as a janitor. He also revealed that every janitor in the installation was part of his conspiracy.

Real Life

 * This is how real world ninja are supposed to have worked.
 * Even if they're not spies, servants can overhear a lot of juicy information from their employers. Both in real life and in fiction, this is often exploited in the form of highly-paid interviews with journalists or in tell-all books.