Trust Me, I'm an X

Stock Phrase saved for characters looking to bill themselves as experts or experienced authorities in dealing with a given situation or problem that has arisen, where X is usually a type of occupation ("Doctor" being the most popular one to use, by far).

Sometimes, a person noting his own occupation is a legitimate argument to get people to take him seriously. When a problem arises in which one's occupational skills and talents can be put to practice, such as after a DIY Disaster, a character noting himself to be a licensed plumber or architect can become pretty useful to have around. In this respect, the cocky hero protagonist who is confident in his abilities and is very skilled at a certain task gets another stock quip or pithy one-liner he can deliver whenever anyone has doubts in him.

However, in many situations, characters may call attention to their occupations in normal discussions, and usually the discussion has absolutely nothing to do with their occupational field, nor does their expertise in said field cast a better light on the subject at hand. Taken to this extreme, the person may not even have the occupation he claims to or even have work in a similar profession.

Very likely to be uttered by the Back-Alley Doctor or the Mad Doctor.

In almost every example, this is, to one extent or another, a type of Appeal to Authority.

Also Known As: Trust Me, I'm A Doctor. This will likely to be the first of his Doctor's Orders in a medical emergency.

Examples of Trust Me, I'm an X include:

Advertising

Lately, there's been a Dr. Pepper ad campaign where "doctors" like Dr. Dre and Gene Simmons ("Dr. Love") use, "Trust me, I'm a doctor," as a slogan. They also give this trope and their own commercials a send-up with Michael Strahan and his "Trust me. I've sent people to the doctor!"
A TV advertisement for the Capital One Venture Card with Alec Baldwin ends with Alec beginning to fiddle with the controls in a plane's cockpit while assuring the pilot, "It's okay, I've played a pilot before."

Anime and Manga

Trafalgar Law on One Piece tends to announce his profession with such a line. Though, it doesn't help that, in addition to being a doctor, he's a pirate. And, OH YEAH, his moniker is "Surgeon of Death," so you might not want to trust this guy too much.
- Actually his medical skills are legit. Considering how he used them to save save the lives of Luffy and Jimbei from certain death.

Comic Books

The above image comes from the 2000 AD strip "Thirteen." His name is Durant, calling himself a doctor like that doesn't really have much to do with preceding or later events in the story, and he's not really a doctor after all.
Matter-Eater Lad of the Legion of Super-Heroes once said, "Trust me, I'm a politician" (Him being a comedic character and politicians being Acceptable Targets).
In Omega the Unknown, the doctor who treats James-Michael says, "Trust me, I'm a doctor," only to turn him into an experiment.
Loki, in the Danish comic Valhalla: "Trust me! I am the god of lies!"
In one of Alan Moore's Abelard Snazz strips, a man who has doubts about trusting the title character with what little remains of his money for planned ruse at a gambling casino is assured, "Trust me, I'm a genius!" By the end of the story, Abelard loses all of the man's money.

Film

From Sherlock Holmes:

Holmes: Madam, I need you to remain calm. And trust me, I'm a professional. Beneath this pillow lies the key to my release.

- Also, when Watson is choking Dredger, he reassuringly tells Dredger, "Relax, I'm a doctor."
The line, "Trust me, I'm a doctor," is said by Dr. John McCabe in The Beyond.
In Muppets from Space, when Ed, examining Gonzo, notices that Gonzo has no nostrils, he asks, "How do you smell?" To which Rizzo the Rat responds, "Awful. Trust me, I'm his roommate."
A non-sequitur example can be found in Slacker, where a woman keeps intoning, "You should quit traumatizing women with sexual intercourse. I should know. I'm a medical doctor. I own a mansion and a yacht."
From Animal House:

Otter: (Rising in a disciplinary hearing) Point of parliamentary procedure!
Hoover: Don't screw around, they're serious this time!
Otter: (aside) Take it easy, I'm pre-law.
Boon: I thought you were pre-med.
Otter: What's the difference?

Another variant from Ghostbusters: "Back off, man, I'm a scientist."
Monty Python and the Holy Grail: Doctors Piglet and Winston try to assure Galahad that they are doctors during his stay at Castle Anthrax.
"Trust him, he's a doctor" was the Tagline appearing on posters for the Rocky Horror Picture Show sequel Shock Treatment.

Literature

In Stephen King's Misery, when Annie is about to cut off Paul's leg to punish him, she says: "Don't worry. I'm a trained nurse." She is, but that doesn't make it much better.

Live-Action TV

Saturday Night Live parodies of The View with Tracy Morgan as Starr Jones would always see Ms. Jones begin every single sentence in a discussion noting, "I am a lawyer" followed by an observation about the news story or subject being discussed that is completely obvious.
The British reality TV show Trust Me — I'm a Beauty Therapist featured eight British celebrities training to become beauticians.
The Doctor Who episode "The Eleventh Hour" had the line, "Trust me; I'm The Doctor."
- Similarly, in one episode, cruise line mogul Max Capricorn's company slogan is "You can trust me, my name is Max." (Twinkle Smile) You can't trust him.
- David Tennant owns a shirt that says, well...
- Matt Smith has said it at least once already, but the truly marvelous example is from 'The Rebel Flesh,' where when his over-foreshadowed 'ganger-clone finally appears it has several lines before the camera finally focuses on it--him, and then finishes up, "Trust me. I'm the Doctor." It's supposed to be creepy, but the episode is suffering from severe Aesop Amnesia, so many viewers are actually kind of relieved he's there.
The CSI episode "The Theory of Everything" has Hodges insist, "Trust me, I'm an expert."
An early episode of Jekyll sees Hyde note, "Trust me, I'm a psychopath."
How I Met Your Mother: "Ted Mosby, architect. Trust me."
Trust Me, I'm A Doctor was the name of a show (and, later, an accompanying book) on BBC Two that focused on the state and quality of health care in Britain. Combining factual reporting and satire, the purpose of the program was to teach viewers that doctors are not infallible and that people should learn as much about their own health care as possible.
House certainly isn't afraid to mention his profession in order to establish his authority or otherwise be a snarker. Once, after bluntly telling a female patient that he wants to inspect her vagina, he tells her, "I'm a doctor, so it's okay."
The True Blood episode where Sam reveals to Sookie that he's a shapeshifter gives us the line, "I'm not the killer, I swear. I'm a shapeshifter."
On Star Trek: Deep Space Nine in the episode "Moving Along Home," Quark assures Odo in a speech, "Trust me, I'm a gambler," explaining why he should take the shortcut in the chula game. Hilariously, it backfires.
Bananas In Pyjamas had a character name "The Rat in the Hat" who's catchphrase was: "Trust me, I'm a Rat".
A Bit of Fry and Laurie discusses the concept of this in a sketch wherein a doctor prescribes tobacco cigarettes for chest problems.

Patient: But these give you lung cancer, bronchitis and emphysema, don't they?
Doctor: What on earth gave you that idea?
Patient: I thought everyone knew that-
Doctor: [laughs] Are you a doctor?

Music

"Trust Me, I'm a Doctor" was a hit single for The Blizzards.

Print Media

British Newspaper The Independent once ran an article on health experts in the media who call themselves "doctors" and may be using that title incorrectly or undeservedly. The title of the article: "Trust Me, I'm A Doctor... Or Am I?"

Video Games

In Dead Rising, after Larry Chiang sticks Carlito on a meathook, he assures to Frank, "Trust me, I'm a butcher."

Web Comics

In The Adventures of Dr. McNinja, Dr. McNinja feels it is important every once in a while to remind people who are having discussions with him that he's a doctor, even while arguing with Death.
In the very first strip of Skin Horse: "The situation is under control. I'm a psychologist."
In 8-bit Theater, the justification that Red Mage often uses for whatever stupid plan that he has is his supposed status as a "fractactical genius".
Penny Arcade: "It's okay, I'm a dentist."

Web Original

Whenever Something Awful cracks jokes about Ron Paul, the sentence "I'm a doctor," or a close variant, tends to show up as a joke reason for why his political platform should be taken seriously.
The online blog Trust Me, I'm a Doctor
Cross-over with Memetic Mutation: Don't worry, I'm/we're from the Internet
A "Dr. Cairo" made a statement along these lines on Twitter while talking to Noah of Tribe Twelve, despite previously establishing that he's a student.
In a Ruby Quest spin-off, "Deja vu Ruby Quest", Filbert gets Ruby before she can even react, and keeps telling her not to worry, even if he has a bonesaw in a hand and a scalpel in the other. If it counts as canon, this spin-off was before Ruby Quest's beginning, so Filbert still has his right hand.

"He says not to worry... He is a professional... He has done this many times before... and the pain... won't last... for long."

Western Animation

Family Guy gave us "Relax, I be a doctor."
Futurama:

"Don't worry, I'm a whale biologist."

Dan Vs.: Hilariously inverted in "Dan Vs. The Animal Shelter".

Doctor: Okay, let's get those pants off.
Dan: Um... I'm here about my face being all scratched.
Doctor: (chuckles) Oh, don't worry. I'm not a doctor.