In Hot Fuzz, all of the supporting cast are famous actors, and all of them did it. Especially well-versed Tropers will note that all of them are also known for playing villains at one point or another, according to the commentary.
In TwistedSamuel L. Jackson is playing the protagonist's foster father and mentor. Naturally, given the types of role Jackson usually plays, he's the killer.
Subverted in Se7en, where Kevin Spacey's name is absent from all promotional material as well as the opening credits, so that his appearance as John Doe towards the end would be a surprise. Unless you recognized his voice when he calls the detectives before his appearance.
Cleverly done in Sleepy Hollow, where the main character, already investigating a crime, is introduced to the town's most important men and the audience is already looking for the guilty among them. They are all played by "vaguely famous" actors: former Maigret (and later Dumbledore) Michael Gambon as the leader, Jeffrey Jones from Amadeus as the reverend, Ian "Palpatine" McDiarmid as the doctor; Michael Gough, formerly Batman's butler and a usual in Burtons's films, as the notary; and Richard Griffiths from Naked Gun 2 as the magistrate. The guilty party is... A conspiracy among all of them! But wait: The real villain behind the ghost is the leader's wife, played by Miranda Richardson.
Used in character in the movie Last Action Hero. Daniel warns Arnold Schwarzenegger's Jack Slater that he should not trust his friend John Practice, because Practice is being played by F. Murray Abraham, notorious for being typecast in bad guy roles, among them the one where "he killed Mozart." So when Practice does betray Slater:
Jack Slater: Danny told me not to trust you. He said you killed Moe Zart.
The movie PSI Love You. Kathy Bates, the dead guy's mother-in-law, agreed to send his letters to his wife after his death. Made somewhat obvious by the fact that she wasn't overly fond of him.
In The Bone Collector with Denzel Washington and Angelina Jolie the killer is the guy played by Leland Orser - a character actor whom you might have seen in several other movies (like Alien: Resurrection and Very Bad Things). This makes it easy to peg him as the killer, although his screentime before his Hannibal Lecture is probably around 20 seconds.
In Kiss The Girls, sharper viewers probably wondered why did they bother to cast Cary Elwes in such a minor role... until the final reveal.
The Clint Eastwood film Blood Work had this problem; Jeff Daniels got second-place billing on the box and in the posters, yet appeared to be nothing more than a minor comic relief character. It isn't very difficult to figure out that he is the killer.
Steve Guttenberg's character turns out to be the killer in Cornered!
In Wolf (1994 movie by Mike Nichols), main character played by Jack Nicholson thinks he's the wolfman behind the murders. The real murderer was James Spader from Sex, Lies, and Videotape, in 1994 also co-starring in Stargate.
Partially averted in State of Play (the American film): A number of characters are played by recognizable actors but Ben Affleck is too famous, too good-looking and too underused to not be important in the outcome. Also, he spends the whole plot being way-too-ready to sacrifice his career, mostly because by doing so he expects to avoid jail.
Many viewers of the 2011 film version of Tinker, Tailor, Soldier, Spy guessed that the traitor was Bill Haydon on the basis that he was played by Colin Firth, while the other suspects were played merely by recognizable British character actors.
Nancy Drew features a seemingly jolly lawyer played by Barry Bostwick. It turns out he was the murderer of an actress from the 80s.
Captain America: The Winter Soldier: The Big Bad of the conspiracy is portrayed by the biggest-name actor to be freshly added to the roster. Robert Redford, in case you were curious. There are still a fair few big-name actors besides the spoiler; it's just that most of them were in roles that had been established beforehand, while Redford hadn't really been seen before.
The director of The Alphabet Killer deliberately made use of this trope to make the audience question who the killer might be by casting male actors who have played killers in other films.
Featured a star from the Canadian TV series The Eleventh Hour. His guest shot was overhyped in CTV commercials, making it obvious he was the killer when he failed to show up almost until the end. But then, CTV does this a lot. Cynthia Nixon's appearance on an episode of Law & Order: SVU, for another example.
Aversion: Wil Wheaton appeared on an episode, bearded, homeless, and crazy. Not recognizable (unless you saw the guest star name at the beginning) or guilty.
Stephen Baldwin was in the same episode as the lead suspect for the other case, about a serial rape-murderer. He had two scenes, and wasn't guilty, dismissed as a suspect halfway through the story. His first scene didn't even give him dialogue.
Also played with in an episode that guest starred Roger Daltrey. He did it, but his character spent most of the episode disguised as several other people. The guy you would have recognized did it, but he was unrecognizable.
CSI is very guilty of casting actors that are go-to TV bad guys as the eventual killer. It's pretty simple to pick out whodunnit if you've watched enough TV (especially 90's dramas like The X-Files. More than once they've cast two "that guy" actors in an episode, and more likely than not they both did it.
Pretty much everyone who was in any way interested in iCarly, knew that Nathan Kress' appearance on CSI was as a bad guy.
Averted again in "Rashomama" when Ray Wise, who has played a killer and the Devil himself was only a suspect for a short time. The same episode also had soap opera actress Rachel Miner and Big Love star Amanda Seyfried. Which, if either of them did it? Well, they both participated, with help from two others.
Michael Westen appears in an episode as part of a convict team fighting fire in the Everglades, while the CSI team is there investigating a different case entirely. He later takes Alexx hostage and escapes.
MarkPellegrino guest-stars as a helpful neighbor giving eyewitness evidence of the killer leaving the scene of the crime, in hopes of getting a reward. He did it, and framed the other guy for a past murder to boot.
Played with in an episode where retired tennis champ John McEnroe is accused of murder: the killer turns out to be a guy who looks like him...also played by McEnroe.
Another episode featured "magician" and professional poser, Criss Angel. When the team suspected him early on, it seemed obvious he wouldn't be the killer. However, by the end of the episode, he had performed almost all of his signature tricks. Oh, and killed someone.
Also played with in an episode that had Kid Rock being suspected of killing an employee who leaked his yet-to-be-released album. He didn't do it, the leak was a Viral Marketing ploy orchestrated by him.
"Second Chances" had 2 straight, 1 subversion, 1 aversion - It looked like Pat Monaghan from Train was the killer - it was his car that ran over the vic. It was his girlfriend and the vic's girlfriend (Kim Kardashian and Vanessa Minnillo) taking drug users off the street and insuring them for 2 years, then killing them for the life insurance, Pat was due to be the next vic they also interviewed La La Vazquez as a suspect, wasn't her.
One episode featured two well-known actors. Of course, they had both done it.
Exception: an episode with Wil Wheaton (again) and Christopher Lloyd. Neither did it.
Another: Bill Nye the Science Guy getting called in as a consultant, and the criminal was someone completely unrelated.
When Nicholas Hoult suddenly materialises halfway through episode 1 of BBC crime drama Wallander (and starts hogging all the screen time) it was only a matter of time before the bloodied axe shows up under his bed.
Sometimes subverted (one episode managed to bring it down to 'Narrowed It Down To The Person I Recognise As Playing Villains by hiring two well-known actors), and sometimes self-subverted through the Retroactive Recognition issue mentioned in the trope description (for example, in one episode Orlando Bloom showed up as 'guy who got run through with a pitchfork').
We could fill this page entirely with Law & Order examples. It's pretty much S.O.P. for L&O shows: if the feature guest star isn't the defense attorney, the victim, or the first suspect, he's the perp. On Law & Order: Criminal Intent, though, it's often obvious who the killer is right from the start as the show is about how the detectives will catch them, rather than whodunnit.
In earlier episodes like "One" and "Jones" and later ones like "Major Case" and "Family Values" we know the killer from the teaser, but usually we don't.
In an episode of Law And Order: Criminal Intent, Stephen Colbert plays a graphologist hired to authenticate some documents, only to find out that he forged them, and committed the original murder. This was before Colbert's show began, but he was already well-known as a reporter on The Daily Show and for Strangers with Candy.
One episode of Special Victims Unit managed to avoid this by having three well-known guest stars (Bob Saget, Chris Sarandon and Catherine Bell) so it wasn't immediately obvious who the killer was.
Yep... another Law & Order: Criminal Intent entry. They interview the woman who ran the prime suspect's foster home, Whoopi Goldberg (with short hair, no less). Guess who's behind the whole thing?
A well done example is the episode of Law & Order: Special Victims Unit featuring Martin Short. It's never in question that he's the guilty party, and the entire episode is a battle of wits between Short and the detectives as he taunts them to prove it.
Also, the celebrity unsubs are sometimes under so much make-up that it takes a few minutes before Hey, It's That Guy! kicks in. Prime example: Jamie Kennedy.
A similar SVU example involved guest star Jerry Lewis. Producers must've been particularly aware of the trope this time as even the promos gave away that he did it, and indeed the crime ultimately committed by his character was done right in front of the eyes of the star detectives — the episode's plot revolved instead around tension leading up to the crime, whether or not he was justified in his actions and whether or not mental incompetence played a role.
Just plain averted in the episode Trade with guest stars Matthew Davis and Stephen Collins. Neither one of them did it.
In "An Evening With Kevin Smith 2", he says that he wanted to play "the guy who leads them to the guy, who leads them to the guy, who leads them to the guy that did it". And he did.
Also averted in an episode of SVU in which Karen Allen is the murderer's wife, but played straight in an earlier episode of the original Law & Order in which Allen is the killer.
In a SVU episode, Eric McCormack played the killer's father. He confesses and everything!
One SVU episode, in quick succession, had the detectives talking to Bobby Flay, Mark McGrath, and Jesse Palmer, all playing Expies of themselves, about halfway through the episode. However they are all past victims of a malicious female rapist that had not reported it for some reason. While the actual rapist was played by the relatively unknown actress and Olympic bronze medalist, Estella Warren, her accomplice and mother, was played by none other than Wonder Woman herself Lynda Carter.
Subverted: One episode of Law & Order: Criminal Intent featured Brent Spiner (Lt. Cdr. Data) as one half of a pair of married psychologists. They were both arrogant twits, but neither of them was the killer.
An inversion: One episode of SVU in which the guest star was Lewis Black as a Howard Stern like radio-DJ. He was never a suspect, but later in the episode, he gets shot in the shoulder by the culprit's mother. The jury acquits.
Not entirely, as Ricky Ullman, Maggie Grace and Dana Delany were also present as Perp, Victim and Shooter of Lewis Black respectively. It was basically Ullman's "Look at me, I'm not chained to Disney, I have range" casting reel.
The next to last episode of the 11th season of SVU has an interesting example: While the perp is known from early in the episode, his father shows up late in the episode and is played by Raymond J Barry, who's seemingly too ubiquitous to JUST be the perp's dad. Not surprisingly, the father was abusive and conspiring with his son.
Another Criminal Intent subversion: Rip Torn guest starred in one episode as a rather cold, unfeeling, and downright unpleasant multi-millionaire who, despite being mean (and despite being portrayed by the big-name guest star), wasn't involved with the murder.
And another: John Glover not only got to be creepy and suspicious in his appearance as Goren's forensic psychology mentor, he also got to be completely innocent. At least the first time he was on.
A semi-subversion in a 2010 SVU had 4 famous (from 25+ years ago) guest stars: Ann-Margaret, Jaclyn Smith, Morgan Fairchild and Susan Anton. Only one of them did it. And in the show, she's no angel.
Yet another Criminal Intent episode; it featured Dylan Baker, normally a Hey, It's That Guy! character actor as he's been in everything, including three different characters in the mothership show. However, the previews for the episode pointed out that Dylan Baker would be guest starring, somewhat unusual for a character actor to be promoted this way. And yes, he did it.
Double Subverted in another 2010 SVU episode, where Henry Ian Cusick is not only cleared early in the episode, but doesn't even appear again...until the next episode, in which he is the culprit.
Subverted in the SVU episode Wet which had David Krumholtz from Numb3rs and The Santa Clause as an Absent-Minded Professor who grow poisonous mushrooms and was obsessed with water right seemed like a slam dunk as a perp. Plus it also hade Rosemary Harris who played Aunt May in the Spider-Man movies as a Rich Bitch who ran the charity were victim was given the poisoned Mushrooms. Add to that the special guest ADA for the episode was played by Paula Patton from Precious and the defense attorney was played by Michael Boatman from Spin City. Yet none of them was the kill, however one of them came off as worse than the actual murderess, and was responsible for her behavior.
The SVU episode Mask, which has Jeremy Irons as a sex addict turned psychologist who specializes in treating them... turns out to be a good guy who helps the main characters after some plot dithering, and also turns out to have NOT committed the terrible crime that he thought he had 20 years ago, namely raping his daughter in a combination of alcoholic blackout and irresistible impulse (it turned out to have been her best friend, and it was consensual, but his daughter, a lesbian, was also in love with the girl and never forgave her father for breaking her heart.
Subverted in the SVU episode Angels: Will Arnett plays a guy involved in a child sex tourism ring, but he's not the main perp. He's not even a pedophile, just a trafficker.
Played with in the Criminal Intent episode "Malignant". Hey, It's That Guy! Stephen Toblowski, a character actor who is recognizable enough to qualify for this trope, plays a pharmacist who, it turns out, has absolutely nothing to do with the drug-delivery hijacking/double-murder that opens the episode except peripherally. That said, it turns out that he's scamming his customers by watering down his drugs, thus quadrupling the money he's making on each drug shipment.
Happens so often on Castle that lately they've taken to casting at least two familiar faces an episode, so even though you know one of them did it, they at least keep you guessing between which.
Robert Picardo was also in an episode of Pushing Daisies as a detective. He hadn't committed any crimes there either. Though Ethan Phillips also appeared and WAS the guilty party.
"One Man's Treasure": You got Mrs. Ari and Miss Farrell over the corpse of a two-timer. So one of them did it, right? Nope, turns out to be Principal Wood, only slightly unrelated to his two-timingness.
For the most part Castle seems to enjoy zigzagging this trope.
William Mapother himself shows up in "Disciple". He did the killing, but he's not the "disciple"; another recognizable actor (Annie Wersching) takes that spot.
The series largely averts this by having a habit of guest stars as innocent characters and usually having two or three recognizable but not super-famous character actors in guest roles. It can be played straight, though...
The first episode has the father of the kidnapped and then murdered young man played by Don S. Davis — who spent eight years on Stargate SG-1 as Gen. Hammond. He did it.
One of the season finales had the guy who played Cameron in Ferris Bueller as a bank robber. Turns out he was being forced into it; the real baddies had his wife held hostage.
Double subverted in a different episode guest-starring Rachael Leigh Cook as an old flame of Shawn's who agrees to go on a date with him...the same day he is taunted by a clue-leaving serial killer. Cook ends up nearly being a victim; the killer turns out to be played by Ally Sheedy, who the viewer had not seen yet, and didn't even realize until later had been hiding in nearly every scene of the episode.
Saul Tigh recently showed up as a grizzled old fisherman and was promptly ignored by the main cast for the majority of the episode. He did it. Although, to be frank, you have to have watched Battlestar Galactica (Reimagined) to get it. Otherwise, he's just another character actor.
Surprisingly subverted with Joey McIntyre (yes, that Joey McIntyre) since he played a police officer new to the precinct and Shawn kept going on about how the perpetrator, a vigilante taking down members of a crime syndicate, had to be someone inside the SBPD. To be fair, though, it was a comic book themed episode and you don't have to be a fan of the genre to realize the reporter in glasses would turn out to be the superhero.
Subverted in the season 7 premiere. Jake Busey shows up as one of two security guys (the other one we've seen already in the episode). A few minutes later, Busey shows up pointing a gun at Shawn and Gus. Turns out he's FBI, having infiltrated the company in order to investigate the man he was guarding earlier.
Played with to hell and back on the 100th episode, which was based on Clue. Three guest stars from the Clue movie (Leslie Ann Warren, Christopher Lloyd, and Martin Mull), and three not (Garret Morris, Curt Smith, and Steve Valentine). What made it particularly apt was that no one committed the crime featured in the episode, and the final culprit - who committed a five-year-old cold case - was voted on during the episode, with multiple possible endings filmed. The east coast and west coast saw different killers.
In an episode of Strong Medicine, a flood of patients from a train derailment caused by a car on the track was followed by a frantic and confused young woman coming into the hospital. Nothing special, except that it was Delia Fisher from My So-Called Life. She did it, but she didn't know she did it.
The same actress shows up in Rizzoli & Isles as an assistant of the body of the week. A short cameo at the beginning, and then nothing until Rizzles realizes that the name of the killer's video game alter ego translates to "underling" or "assistant" in a Scandinavian language.
Elementary: In just the course of one season of 24 episodes, roughly half involve examples of reasonably well known actors and actresses as the only recognisable potential suspect, with the majority of those being played straight by them performing the crime.
In Rat Race, Molly Price, who played a large role in Third Watch as well as numerous other tv shows and movies, showed up very early in the episode as a secretary. She did it.
An episode had Daveigh Chase (Samara Morgan from The Ring) guest star as one of the suspects. Guess who the killer was?
There were Reed Diamond he did it in the season 7 episode "Forensics", StevenCulp who also did it in the episode Jurisprudence, and Loretta Devine in Soul, and yes, she did it too, among others.
Another episode had Barry Bostwick as the killer. Also doubles as Stunt Casting, as the original murder took place after a midnight showing of The Rocky Horror Picture Show in the late 70s. Though they actually he it was him from the get go, as he played the aged already imprisoned serial killer.
As soon as Daniel Baldwin showed up, you just knew he was the perp. He was so effective in this role, he stayed on for 7 episodes.
Episodes with really, really old cases from the '30s and '40s often had the perp, if they were still alive, played by someone well-known, including Peter Graves, Ralph Waite, Orson Bean, and Piper Laurie.
Dylan Baker was accused of his wife's murder in an episode of The Good Wife but he was acquitted. At the end, he reveals he did do it.
Ironically, an episode of it seems like Reed Diamond did it, but in the end Allison finds out that the 'victim' is still alive and a few years younger than in her dreams, so she understands he might do it, despite being anything but a killer to this point, and warns him so hopefully he won't do it.
"Mr. Monk and the Girl who Cried Wolf" featured Emma Caufield (the former vengeance demon Anya from Buffy the Vampire Slayer) as Sharona's creative writing teacher. She hadn't "done it" yet, but she was about to.
Subverted in "Mr. Monk on Wheels," in which Bradley Whitford's character Dr. Dean Berry is not the killer - who is his assistant Sarah Longson (Pamela Adlon). Rather, Whitford's Berry is the
"Mr. Monk and the Kid" had a well-known actress in a minor role, and as soon as the audience heard her and said "Hey, that's Shego!" they knew Janet Novak was guilty.
"Mr. Monk Goes to a Fashion Show," where Malcolm McDowell is Julian Hodge, and gets Special Guest Star billing. In the episode, one of his models is killed. Just do the math once you see his Berserk Button.
Averted in "Mr. Monk and the Red Headed Stranger," with one of the series' first advertised guest stars. In it, Willie Nelson gets accused of shooting his road manager by an Eye Witness who couldn't have possibly done it because she is blind. She isn't and she did it.
Played straight with Brad Garrett as "Honest" Jake in "Mr. Monk Buys a House".
David Strathairn in "Mr. Monk and the Genius" - whose character we are introduced to before he kills his wife.
With Steve Valentine in "Mr. Monk and the Magician", more so since we see that this magician is involved in drug trafficking.
Wonderfully subverted in "Mr. Monk Joins a Cult." By this point in the series it was common for the highly-billed guest-star to be the killer, so in the end Howie Mandel's Ralph Roberts actually turns out to not be the murderer in the episode and it's revealed to really be the eyewitness to the murder who appeared at the very beginning.
Also subverted in "Mr. Monk and the Bully," where Noah Emmerich's role as Roderick Brody is billed as special guest star, but he instead gets framed up for a stabbing by his wife's evil twin sister played by Julie Bowen. So technically the actress you recognise did it but not the character.
Also subverted in "Mr. Monk Makes the Playoffs," which features Bob Costas as himself. He only serves as a plot point and is not involved with the crime in any way.
An episode featured Thomas F. Wilson as the victim's boss. You best remember him as Biff Tannen from Back to the Future. He turned out to be the killer.
Another had Adam Baldwin as an FBI agent looking for a mob killer and protecting Brennan from a hit man. He was the killer and the hit man.
A third episode has a People Who Died On Buffy reunion where both major lawyers and the lead investigator were all characters who died on Buffy. I was so sure one of them was dirty!
Subverted in a sense in one episode, where the killer was not the mildly famous person (Spencer Breslin); however, he did turn out to be the father of all those babies, including the unborn child of the victim.
Subverted fabulously in a an episode where Robert Englund, who's famous for playing Freddy Krueger in the A Nightmare on Elm Street movies, played a janitor. He also did not do it. Furthermore, the first crime featured the story of a cannibal who killed his victims for their delicious flesh. Robert Englund's character offers Bones and Booth some delicious ribs.
As opposed to the Castle ep above, Miss Farrell did do it in "The Man in the Mud" ... but the episode also had Tom Friendly, Delia Fisher, and Joey Lawrence's little brother to choose from.
The season 5 episode "The X In the File" featured Dean Haglund, who played a recurring character on The X-Files (Langly, one of The Lone Gunmen). He did it.
Averted in one episode, where it turns out Xander Berkeley DIDN'T do it for the first time in his career.
A more subtle one in the second Gravedigger episode. Fans of The Wire will know Rhonda Pearlman isn't going to show up just to cameo in a couple of lawyer scenes.
Even Battlestar Galactica is guilty of this, in a roundabout way. Lucy Lawless and Dean Stockwell both appeared as supposedly one-shot characters before being outed as Cylons.
In the case of the 1st mentioned character, the reveal was at the end of the initial appearance. The 2nd wasn't actually revealed until a subsequent appearance.
The West Wing had Glenn Close show up during a search for a Supreme Court Justice.
Semi-subversion in that Close's character was up against Bill Fichtner for the job. The twist was that the White House staff found a way to hire both of them.
One episode had Lucy Lawless play a grieving woman looking for her husband. ...until about halfway through the episode when she's revealed to be a spy looking to kill the man Michael unwittingly guided her to.
Subverted in the Season 1 cliff-hanger finale, where Richard Schiff shows up as a guest star, and is killed off after just a couple of minutes of screen time. The DVD commentary says they specifically hired a big name so the audience would see him as the ultimate bad guy—they wouldn't pay a big star like that to be just a one-shot flunky.
In the season 5 finale, Michael is running a CIA op with Dean Cain, Kristanna Loken, and Maxwell Terlecki, and one of them is a mole. Dean is still Super-good and Kristinna is aiming to take out the forces of good.
Sometimes it's deliberately averted. Several episodes had recognizable faces as Mike's clients, including Frank Whaley and Jean Louisa Kelly, so when Jere Burns shows up as a client, you don't suspect him. Turns out he's the guy behind the organization that burned Mike.
Especially since, like nearly all Columbo murderers, he's shown committing the crime before Columbo even appears.
Subverted in one Columbo where we see Robert Vaughn cleaning up a murder scene after the fact, and assume he did it. He didn't. In fact, he turned out to be the next victim.
On Masterpiece Theatre's 2009 adaptation of Agatha Christie's "They Do It With Mirrors," the perpetrator is played by Brian Cox, otherwise known as Stryker from the second X-Men film, or Ward Abbott from The Bourne Series films, or the original Hannibal Lecter.
NCIS had a late first season episode that guest starred Adam Baldwin, JulieBenz, and DougSavant (albeit this was the season before the later show started). Though Adam Baldwin is never a suspect. Subverted in the fact that NONE of them are guilty - the murder of the week was actually a suicide.
Inverted in the episode "Singled Out" with Misha Collins accused of murdering a female navy officer. He's guilty of carjacking her, but not her murder.
In another episode, the team got a lead on their case from a bartender played by Claudia Black. Guess who did it?
Life On Mars did this a lot; then again, the week's crime case was usually the episode's least important plot.
Averted on The Closer: Connor Trinneer plays one of the suspects but is quickly cleared within the first scene he appears in.
Played straight with Philip Stroh. Attorneys are relatively few and far between on this show (mostly because Brenda is very good at convincing the suspects that they don't need one), so when one not only shows up, but is also played by Billy Burke, you kind of assume he's gonna be important. Stroh turns out to be his serial raping client's much more evil accomplice, and eventually becomes Brenda's That One Case.
Furuhata Ninzaburo takes this trope Up to Eleven: the criminal is played by a famous face each time, and at least twice Furuhata faces off against actual celebrities: a No Celebrities Were Harmed version of baseball star Ichiro Suzuki (who, btw, flat out refused to have his character's name changed) and the entire J Pop band SMAP.
LOST loves to play around with this. One good example is the actor Doug Hutchison, most famous for his role as the sadistic guard in The Green Mile. He briefly appears in a season 3 episode. Then he briefly appears in a season 4 episode. Then he plays a central role in five episodes in season 5.
Every single god damn episode of the The Mentalist. If the actor is familiar but playing a bit role, automatically expect them to be the murderer or the mastermind of the murder no matter how unlikely. 9 times out of 10, you'll be right.
In the Supernatural episode "Clap Your Hands If You Believe...", a red flag went up as soon as Robert Picardo came on screen, acting all lame and insignificant. Obviously, he was the villain.
Come on, as if you didn't knew that Alan Tudyk would play something better than just an architect on Dollhouse.
In the pilot episode of Blue Bloods, Corey Feldman is there for 30 seconds as a doll reviewer(!) and to create the illusion of 'they caught they bad guy real early' until we realize we've been mislead by the Stunt Casting.
Averted by an episode of the remake of Hawaii Five-0, in which D.B. Sweeney is a murder suspect. It turns out his wife did it.
This is generally averted on Criminal Minds, which makes frequent usage of Hey, It's That Guy! actors as supporting characters, but rarely has them turn out to be the Unsub, except in the cases where a well-known actor is cast specifically to play a major villain whose identity is shown from the beginning of the episode. Other times while the actor may be well known, the killer's face isn't seen until his arrest.
Most notable subversion was in "The Performer", where Gavin Rossdale's character, musician Paul "Dante" Davies, was suspected as the killer for the entire episode. It turned out to be a superfan with the help of his manager, who was using the murders as a way to promote his album.
Played straight in "Uncanny Valley" if you've paid attention to the credits. Jonathan Frakes was billed to appear in the episode, but doesn't appear until the end when the team figures out that he's the one who induced the case's UnSub to kidnap women in the first place, because he took away her dolls.
In the first season, the murderer was the character played by Harry Hamlin, of L.A. Law and Clash of the Titans fame—only a recurrent character.
Averted in the second season: Ambitious rich guy played by Steve Guttenberg (Police Academy, 3 Men and a Baby, Cocoon) was behind an evil deed that corrupted the real murderer behind the story arc.
Another episode had Kristen Cavaleri as a lesbian cheerleader in an episode where gay students were being outed. Turns out she was the outer but it was really just a scam because she only outed her girlfriend who she wanted to come out.
In Hot In Cleveland,Betty White is told of a murder, and when she says "Why are you telling me that?" the person telling her says that she always figures out who the killer is in CSI: Crime Scene Investigation in the first three minutes. Betty White says that it's due to knowing who the guest stars were - you don't hire Tony Danza to play "a hotel concierge with three lines."
A Nero Wolfe Mystery played with, or possibly completely inverted, this trope: The supporting cast stayed mostly the same from episode to episode, but except for a small core cast the actors played different roles in different stories — so while you can nearly always recognise "the guy" (or "the gal"), it's of no use to you in jumping to the solution of the case, since the murderer one week might be the victim the next week and just some background supporting character the week after that.
Carnivŕle: The plot in Babylon city involved the murder of one Carnie and the others looking for the murderer among the Babylonians. They eventually decided to exact their justice in John Hannah's character (The Mummy; Sliding Doors). Hannah then confesses.
Breaking Bad, of all shows. Walt and Jesse are going to meet a super-mysterious drug dealer to handle their bulk amount of meth at a fast food restaurant and the manager asks them if they're doing well. Gus Fring's actor is Giancarlo Esposito, not hugely famous, but prolific nonetheless.
Poirot averted this in their adaptation of Appointment with Death. When one sees that the victims husband is played by Tim Curry, one starts to suspect him only to have his son being played by Mark Gatiss and John Hannah playing their doctor friend.
The adaptation of Sad Cypress seems to be aiming for this, featuring Paul McGann and Rupert Henry-Jones among the guest cast. However, the fact that Phyllis Logan is playing a character who seems to be a complete non-entity practically screams "She did it!"
Played for Laughs on 30 Rock when Liz convinces Jack to "Mamma Mia!" the three men Jack's private detective has come up with who could potentially be his father. They lure the men to New York under the pretense of having won a contest, and when they get there, instead of hijinks ensuing, we immediately find out that one of them is Korean and another had his genitals blown off in World War II. The third is Alan Alda.
In an adaptation of 'The Secret of Chimneys', the ITV broadcast 'Marple' episode saw Edward Fox cast as the murderous Lord Caterham. The actor in question has a face which is instantly regognisable to most Brits, especially the age-group likely to enjoy Agatha Christie adaptations.
Not a detective show, but in How I Met Your Mother Ted is given a choice of three women to date - Barney shows him their photos before Ted sees the girls. While the other two are not so familiar, one of the pictures is of AnnaCamp, and of course she gets chosen.
Subverted in Hannibal. You'd think they wouldn't cast Jeremy Davies unless it were as the killer, and the show doesn't usually zig-zag a lot in that respect, but sure enough, he turned out to be a patsy.
It was an example of this that led many to believe that WWE NXT might be rigged. Of the six rookie Divas, only two were given any kind of storyline outside of competing for NXT, Kaitlyn and Aksana. (Interestingly, these two are most often considered the two worst of the six.) Aksana, who was born in Lithuania, was given an angle where she had to marry her pro Goldust to obtain a green card, and Kaitlyn was in a love triangle with her pro, Vickie Guerrero, and Vickie's boyfriend, Dolph Ziggler. Aksana stayed in the competition until her storyline marriage with Goldust was over, than was eliminated almost immediately after. This left Kaitlyn as the only Rookie with any type of storyline. When she eventually won the competition, it appeared that WWE forced Kaitlyn into becoming the Girl I Recognize, making her the only one visible outside of NXT (which is a web-only show) and thereby leading fans to vote for her (since she was the only one they probably knew anything about).
A kind of double subversion: Johnny Young Bosch was also playing the protagonist, meaning that getting him to play an insignificant character would be making more use of him rather than wasting him. However, the protagonist is almost a Heroic Mime, so having him play another important character would make sure that he wasn't wasted.
Grampa: I say we call Matlock. He'll find the culprit. It's probably that evil Gavin MacLeod or George "Goober" Lindsay.
Family Guy blatantly points out this trope when they have an episode of a random crime drama playing. With the main characters questioning who committed a crime, then nodding and pointing to the "With Special Guest Star Jimmy Smits" part when it pops up in the opening credits.
The same show averted it with the episode And Then There Were Fewer. The suspects were mostly recurring characters, aside from the first victim and a new character played by Ashley Tisdale. It turned out the culprit was Diane, a recurring newscaster. Tisdale's character was in fact a victim