Cameos in movies come in all shapes and sizes. When done right, a cameo can take audiences by surprise and thrust the plot forward in interesting and unique ways (like Leonard Nemoy's appearance in 2009's Star Trek as Spock Prime). When done wrong, it can come across as unnecessary fan service that just feels out of place (like David Hasselhoff in 2017's Baywatch).

Sometimes a cameo can be random but fun (like Danny Glover's appearance opposite Mel Gibson in 1994's Maverick, complete with a hint of that classic Lethal Weapon score), sometimes it’s random and odd (like, well, David Hasselhoff in Guardians of the Galaxy Vol. 2), and sometimes it’s simply perfect (see: Hugh Jackman in X-Men: First Class). 

Cameos don't last long enough to influence a film one way or the other. They're usually good for a chuckle with no real harm done to the overall story.

However, then there are some that break that mold by either being so amazing that they steal the show, or so awful that they bring the film to a screeching halt, knocking audiences out of the world the film was trying to create.

Here are the 7 Celebrity Cameos That Completely Ruined Their Movies (And 8 That Stole The Show).

Stole: Mike Tyson in The Hangover

The Hangover is a great movie that is still every bit as good today as it was in 2009 when it was released. The film received so much praise from critics and audiences that it would go on to earn $467 million worldwide, making it one of the biggest films of the year and spawning two sequels (that were, sadly, pretty bad).

The original film had everything going for it. A unique and hilarious premise, snappy dialogue, and star-making performances by Bradley Cooper, Ed Helms, and Zach Galifianakis. The film's ace-in-the-hole, however, was an amazing cameo by Mike Tyson.

Tyson shows up relatively early in the film and reveals himself as the owner of the tiger locked in the guys' hotel room. The cameo is completely unexpected, yet it absolutely works. Tyson is hilarious in the role, and his knockout punch to Galifianakis is simply the stuff of legend.

Ruined: Matt Damon in Thor: Ragnarok

Matt Damon as Loki

The opening of Thor: Ragnarok sees the God of Thunder imprisoned by Surtur. After some witty banter between the two, Thor escapes his chains, defeats the fire demon, and returns to Asgard with said demon's crown in tow. Upon his return, Thor comes across a play depicting Loki's supposed death from Thor: The Dark World.

The scene has all the makings of greatness. Of course Loki would be watching a dramatic re-telling of the time he faked his death. The acting in the play is cheesy and over the top and the sight of Sir Anthony Hopkins lying on a couch eating grapes is simply hysterical.

Then the film cuts to a close-up and reveals Matt Damon playing the role of Loki, and the result is just odd. The sight of a well-known A-lister (seemingly playing himself) on Asgard just doesn't compute, and wasn't necessary. The scene was perfectly fine without it.

Stole: Bob Saget in Half-Baked

Bob Saget as Danny Tanner in Full House

From the late 1980's and throughout most of the 90's, Bob Saget was the wholesome face of America.

Between his role as clean-cut single father of three Danny Tanner on Full House (who was always down for a heart-to-heart talk with any of his daughters) and his hosting gig on America's Funniest Home Videos, he was the beloved father figure to an entire generation of kids. Then he teamed up with Dave Chappelle in 1998's Half Baked and that changed forever.

In the film Chappelle plays Thurgood Jenkins, a marijuana dealer and user who eventually finds himself in rehab. While describing his drug of choice to a group of addicts, Jenkins is interrupted by none other than Bob Saget who claims, "marijuana is not a drug." What he says next cannot be quoted here, but lets just say it hilariously shatters Saget's wholesome persona.  

Ruined: Will Smith in Winter's Tale

Will Smith holding a Neuralyzer in Men in Black

Boy does Will wish he had a de-neuralyzer for this one. Winter's Tale is a 2014 film based on the book of the same name. It stars Colin Farrell, Jennifer Connelly, and Russell Crowe, and takes place in a world where angels and demons exist.

To make a long story short, Crowe's character (a demon) tries to kill Farrell's character, but Farrell manages to escape the five boroughs of New York City, thus putting him outside of Crowe's jurisdiction (yes, you read that right).

In response, Crowe visits Lucifer and requests permission to pursue Farrell. The scene starts in darkness and audiences can hear Crowe speaking to a demonic voice.

Then the room brightens revealing the devil himself, played by Will Smith. The cameo is abrupt and feels out of place given Smith's reputation and star power. Audiences didn't see "the devil", they saw Will Smith. It grinds the movie to a halt.

Stole: Margot Robbie in The Big Short

Margot Robbie drinking in a bathtub in The Big Short

The Big Short is a well-written, well-acted film about the United States financial crisis of 2007-2008. The film is filled with financial and Wall Street jargon destined (and pretty much designed) to confuse the average movie-goer.

To work around this little issue, director Adam McKay cuts in a few cameos featuring celebrities speaking directly to the audience and breaking down some of the more confusing terms.

The best cameo by far is the one featuring Margot Robbie. After a brief introduction by the film's narrator Ryan Gosling, there's a quick cut to Robbie sitting in a bath tub.

The actress explains subprime loans coolly and rationally while sipping champagne in a scene that fits in perfectly with the film's overall aesthetic. To top things off, Robbie ends her two-minute cameo with a quick "Got it? Good. Now f*ck off" to the audience. It's simply perfect.

Ruined: Matt Damon in Interstellar

Matt Damon in Interstellar

Matt Damon makes his second appearance on our list in yet another surprise cameo that pulls audiences right out of the film. This time it's Interstellar, Christopher Nolan's deep-space drama about humanity's last-ditch effort to leave behind a dying Earth.

In the movie, Matthew McConaughey and Ann Hathaway lead a team of astronauts to a distant star hoping to find a habitable planet to call home.

The team goes in search of Dr. Mann, a scientist who traveled to a planet ahead of the McConaughey-Hathaway team to see if it can support human life. The team reaches the planet and opens up a cryostasis chamber where they awaken the doctor, played by Matt Damon.

This is yet another cameo diminished by the actor's star power. Damon is simply too well-known to be put in such a role. Casting a relatively unknown actor would have made the reveal much less jarring.

Stole: Johnny Depp in 21 Jump Street

Johnny Depp grinning in The Rum Diary

One of the unwritten rules that comes with adapting a television series to film is the film must feature a cameo by an actor from the original series. The aforementioned Star Trek and Baywatch, for example, feature cameos by original cast members, to varying degrees of success. When it comes to this type of cameo, no film did it better than 21 Jump Street.

Johnny Depp became a household name following his role as Officer Tom Hanson in the original series, so his appearance in the 2012 film wasn't entirely unexpected, but it was brilliant nonetheless.

With the film's new 21 Jump Street crew facing certain death, Johnny Depp saves the day, removing a disguise and revealing himself as Tom Hanson, thus placing the film within the continuity of the original series. The scene is a great nod to fans of the show, and it ends with a surprise that's too good to spoil.

Ruined: Bruce Willis in Ocean's Twelve

The Ocean's Eleven trilogy has its fair share of ups and downs with the ups primarily coming in the first and third entries and the down pretty much being the second.

In addition to the fact that the second and third acts are rendered pointless by the ending (since, you know, Clooney and Co. had the egg the whole time), the film also features a mind-numbing cameo by Bruce Willis.

Around halfway through the film, Tess (played by Julia Roberts) poses as Julia Roberts in order to try and steal the egg (which means Julia Roberts exists in the world of the film). The film then doubles down on this faulty logic by having Bruce Willis show up as himself.

So Julia Roberts and Bruce Willis both exist in this universe, but George Clooney, Brad Pitt, Matt Damon, and the rest don't? It's a needlessly complicated scene that brings the whole film down.

Stole:  Michael Jackson in Men in Black 2

Michael Jackson in MiB 2

Men in Black is a great action comedy that still holds up today. Men in Black 2 is not. Not only did the film disappoint audiences but it also negated the ending of the original by immediately bringing Agent K back into the fold. The film's saving grace, however, comes in the form of two hilarious cameos by the King of Pop himself.

In the original film, J learns that aliens live among us in secret and that Sylvester Stallone is one of them. The sequel calls back to this joke by revealing Michael Jackson not only as an alien, but as an alien desperate to join the MIB.

Jackson twice speaks to Zed on the phone, pleading with the MIB leader to let him join. The sincerity in Jackson's words as he exclaims, "I can be Agent M!" is simply hysterical and is one of the few highlights of the film.

Ruined: Mark Ruffalo in Iron Man 3

Mark Ruffalo as Bruce Banner in Iron Man 3

Iron Man 3 could have been an amazing film. It was the first MCU film released after the immensely successful The Avengers, starred the MCU's most popular character, and featured what seemed certain to be an incredibly compelling performance by Ben Kingsley as the Mandarin. Then Marvel pulled a bait-and-switch with Kingsley's character and divided the fan base as a result.

The worst part of the film, however, comes during the post-credits scene when Mark Ruffalo makes a cameo as Bruce Banner. While Marvel was clearly going for a fun joke to send audiences home happy, all Ruffalo's appearance did was confuse fans who already wondered why the rest of the Avengers were missing in action while Tony Stark was missing and presumed dead.

A cameo by the Hulk helping Tony to defeat the Extremis soldiers in the film's climax would have been fun. The cameo we got was a major disappointment.

Stole: Stan Lee in Guardians of the Galaxy Vol. 2

Stan Lee - Guardians of the Galaxy 2

For as long as there have been Marvel movies, there have been Stan Lee cameos in them. This is a tradition that goes back long before the days of the MCU when Lee was appearing in films like the original Spider-Man and X-Men trilogies, among others.

He has also appeared in every single MCU film to date, which was interesting at first but became a bit odd seeing as how the films all exist in the same universe.

How can Stan Lee be rubbing elbows with Tony Stark on Earth while simultaneously wooing a woman on Xandar? Lee's appearances caused fans to theorize that he is actually Uatu the Watcher from the comics.

Then Lee's cameo in Guardians of the Galaxy Vol. 2 revealed him as an informant for the Watchers, which means this was Marvel's plan all along, or the studio heard the theory and ran with it. Either way, it's awesome.

Ruined: Keith Richards in Pirates of the Caribbean

Keith Richards sitting with a guitar in Pirates of the Caribbean: On Stranger Tides

In terms of quality, the Pirates of the Caribbean franchise is a bit like a roller coaster. If said roller coaster started at its peak and the rest of the ride was a steep drop. What started out as a hip, funny, action-packed film featuring a gripping performance by Johnny Depp eventually turned into a convoluted mess of a franchise that overstayed its welcome.

Depp cited Keith Richards as the inspiration for his legendary performance as Jack Sparrow in the original film. Then, in an odd example of art imitating life imitating art imitating life, Richards' was cast as Sparrow's father in At World's End. All it took was one simple cameo to kill all of the mystique surrounding the iconic character.

Sparrow was no longer a man of mystery whose behavior bewildered others. He was simply acting like his father. Oh, and his mother is a shrunken head (for some reason).

Stole: Neil Patrick Harris in Harold and Kumar Go To White Castle

Neil Patrick Harris in Harold and Kumar

Harold and Kumar Go To White Castle is a film with a simple premise: two stoners try to get to White Castle, hijinks ensue. The two stoner heroes run into all sorts of trouble on their way to the infamous fast food joint. The absolute best scene in the film comes when the main characters pick up a hitchhiker who turns out to be none other than Neil Patrick Harris.

This was before Harris' return to TV glory in How I Met Your Mother and when he was best known for his childhood role in Doogey Houser, M.D. The two main characters are initially stunned to see the former child actor on the side of the road and quickly learn he is drugged out of his mind and borderline insane.

Harris' performance in the film and the rest of the trilogy is unlike any other cameo on the list, and will go down as one of the best ever.

Ruined: Everyone in Movie 43

Movie 43 cast image

The story behind the making of Movie 43 is much more interesting than anything in the film itself. One glance at the cast list (and all of the major stars contained therein) is a testament to this. How could a single movie possibly manage to juggle the schedules of so many well-known actors?

The short answer: by working around the schedules of those actors. The producers shot the film over the course of several years and the result is a disjointed collection of painfully unfunny segments tied loosely together by a razor-thin plot. Each actor's appearance in the film adds up to little more than a cameo, collectively making it the worst celebrity cameo of all time.

The film was panned by critics and audiences but managed to make $32 million at the worldwide box office, which (considering its budget was $6 million) means it can be deemed a success. Yay?

Stole: Bill Murray in Zombieland

Bill Murray dressed like a zombie and Woody Harrelson in Zombieland

Zombieland didn't need a Bill Murray cameo. It is a well-written, well-acted comedy about the survivors of a zombie apocalypse picking off the undead in fun and imaginative ways. And then Bill Murray shows up (as himself, of course) and brings the film to another level.

The film's main characters find themselves in a seemingly abandoned mansion (dancing to the theme from Ghostbusters no less) when what appears to be a zombie version of Bill Murray appears and attacks. Emma Stone hits him with a golf club and Murray cries out in pain, revealing that he is simply posing as a zombie because "zombies don't mess with other zombies".

The cameo is surprising and doesn't overstay its welcome. It brings the film in a fun, new direction without pulling the audience out of the moment, which is precisely what a cameo is supposed to do and why it tops our list.

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What other celebrity cameos do you love? Are there any others that ruined their movie? Let us know in the comments.