When someone appears on-screen who audiences don't expect, it can make that moment stand out in a special way. Cameo appearances are like inside jokes between the fans and the filmmaker, and they draw the two groups closer like only an inside joke can. Hitchcock and Tarantino are known for making appearances in their own films, while James Cameron likes to let the crew members shine, putting them in front of the camera to leave their own mark on the finished product. Occasionally, however, a celeb is so excited about a particular project that they are happy to be a small part of it, and pop up on the big screen even when we're not anticipating it.

These are the ten appearances that stand out for us. Here are Screen Rant's 10 Best Celebrity Movie Cameos Ever.

Martin Sheen, Hot Shots! Part Deux

It's voiceover versus voiceover, Sheen versus Sheen in this well-known moment from the 1993 spoof-flick Hot Shots! Part Deux. While drifting down the river, a Rambo-esque Charlie Sheen passes his father, Martin Sheen, still in character from the explosive Apocalypse Now on another boat. No strangers to working together, the father and son starred in 1987's wildly successful Wall Street.

As the two approach one another here, the younger Sheen is journaling away until he's interrupted by someone else's journaling, his father's. Without missing a beat, the two rise and yell "I loved you in Wall Street!" in unison as their ships pass, before transitioning right back into their characters. While the scene is short, it's absurdity makes it one of the most memorable movie cameos ever.

Danny Glover, Maverick

Audiences are familiar with the on-screen subtleties of the relationship between partners Riggs and Murtaugh thanks to the four movies that make up the Lethal Weapon franchise. Mel Gibson as the hotheaded wildcard with a chip on his shoulder and something to prove next to Danny Glover's days away from retirement "I'm too old for this shit" attitude was the key ingredient to their legendary on-screen chemistry.

When Gibson and Lethal Weapon director Richard Donner teamed up for 1994's Maverick, they saw an opportunity to do it again. While collecting a debt, Maverick is robbed by an outlaw played by Danny Glover. Gazing at each other like they've met before but can't place where, the trademark '80s score from Lethal Weapon plays before they shake their heads in unison and Glover takes off with the loot.

Matt Damon, Eurotrip

Not only is Scotty's girlfriend cheating on him, she's doing it with the macho frontman of the band playing their graduation party, in one of the most memorable scenes from 2004's Eurotrip.

While watching the band perform their hit song "Scotty Doesn't Know," it slowly dawns on Scott (Scott Mechlowicz) that his relationship is the one being sung about, and the Fiona in the song having sex in the back of a van on Sundays is his Fiona (Kristin Kreuk). The driver of that sex van is no other than People Magazine's Sexiest Man Alive 2007, Matt Damon. Almost unrecognizable with a bald head, nail polish, and tattoos, Damon belts out all the things Scotty doesn't know before viciously making out with Kreuk on stage, an experience she recounts as her most awkward on-screen kiss to date.

Friends with the director, writer and producer from their days at Harvard, Damon was filming a movie nearby but dropped by the set to say hello and, notorious for his incredible sense of humor, ended up in the movie. Recorded by real-life band Lustra, Scotty Doesn't Know peaked at number 53 on the Billboard charts.

Related: Matt Damon's EuroTrip Song "Scotty Doesn't Know" Brought A Woman Out Of A Coma

David Bowie, Zoolander

In the fashion industry, the only thing that matters is your credibility. It's no surprise, then, that as writer, director, and star of 2001 model comedy Zoolander Ben Stiller found it necessary to inject as many beautiful people as possible into the movie's 89 minutes. While many of the cameos are notable, there is one in particular that stands out above the rest, and for good reason.

When the modelling rivalry between Hansel (Owen Wilson) and Derek (Ben Stiller) comes to a head, David Bowie steps in to oversee a sacred duel: The Walk-off. Complete with his own freeze frame, he steps out of the crowd and offers his services. Bowie knows a thing or two about the fashion industry. He's married to model Iman, wrote a song called "Fashion," and is a fashion icon himself; famous for both his music and his various costumes throughout his varied career.

Bill Murray, Zombieland

When life gives you lemons, you make lemonade. That's Bill Murray's philosophy as outlined in this cameo from 2009's Zombieland. Clad in makeup so he won't be recognized as a human by zombies, Murray spends his days playing golf and re-enacting scenes from Ghostbusters in his mansion before being mistaken for a walker and shot accidentally. Confident that he would decline, the filmmakers didn't approach Murray at first, offering the role instead to Matthew McConaughey, among others.

It was Woody Harrelson who pitched the idea to Murray, who fell in love with it and collaborated with writers to make the scene even funnier. Seeing the cast of Zombieland so starstruck by him on screen adds a layer of fandom that almost every audience member can relate to.

Samuel L. Jackson, Iron Man

Fans worldwide lost their collective mind during the post-credit scene from the 2008 blockbuster Iron Man. As Stark returns home, he is greeted by the director of S.H.I.E.L.D, Nick Fury, played by ultimate badass number one Samuel L. Jackson.

Mentioning of the "Avengers Initiative" sent fans into a euphoric tizzy about the potential crossover stories in films to come. The most recent incantation of Nick Fury's character is based on Jackson himself, making him the obvious casting choice. Needless to day, Samuel L. Jackson's uncredited cameo was a hit with audiences, and he agreed to play Fury in eight more projects.

Channing Tatum, This is the End

When talking about cameos, it's impossible to ignore the Seth Rogen and Evan Goldberg love-child that is 2013's This is the End, where every single cast member plays a version of themselves. A party hosted by James Franco is rudely interrupted by a biblical apocalypse that kills off most of the guest list, save for the film's main protagonists.

While the shot of Rhianna slapping Michael Cera across the face is pretty epic, the most memorable cameo by far is near the end of the movie, and comes in the form of Danny Mc Bride's personal sex-slave: Channing Tatum. Attached to the end of a leash, Tatum is clad in a Luchador mask and not much else as he scrambles around at his masters ankles and does tricks like a dog. Referred to as the "gimp", Tatum was allegedly discovered wandering down the highway, and now travels with McBride, who looks like he's straight out of Mad Max.

Tom Cruise, Tropic Thunder

Touted by many as be the funniest character in the film (and the role that saved his career), Tom Cruise's turn as Les Grossman in 2008's Tropic Thunder shone a positive light on his career when he needed it most. Cruise not only played the portly Hollywood hotshot, he developed the look and dialogue for the character as well, though Justin Theroux is credited by co-star Bill Hader as perfecting the more filthy lines. The prosthetic hands, dancing, and fat suit: all his ideas.

In fact, his special effects makeup was so authentic looking that many audience members didn't even recognize that it was Cruise underneath. Requiring multiple swaps a day, the fat suit was so overwhelmingly hot that it would be soaked through with sweat by lunch. Shimmying his way across the screen in an individually hand-punched hairpiece (that took six people to make) it is rumored that Cruise based his character on a Hollywood executive he had a falling out with.

Bad Anon, Wreck-it Ralph

What once was called "High Score" and "Joe Jump" became the 2012 Disney powerhouse Wreck-It Ralph, a movie so loaded with references big and small that, if you so much as sneeze, you'll miss one. Inspired by elements of Donkey Kong and Rampage, Wreck-it Ralph is a temperamental brute who smashes his way from A to B, but only during the course of his day job duties inside the video game Fix-It Felix. John C. Reilly voices the golden-hearted thug who's trying to change his violent ways by attending Bad Anon support group meetings, surrounded by the likes of Bowser, Doctor Robotnik, M. Bison and Zangief, who gives a passionate speech about what it means to be a bad guy.

Because Disney was able to obtain the rights for many of the characters on screen, several of the meetings' attendees are voiced by the original actors. During the course of production, the team were encouraged to visit candy factories and play hours of video games in order to get a sense of the characters and environments they'd be creating, confirming our suspicion that this is a movie for kids, by kids.

Bob Barker, Happy Gilmore

Bob Barker proves that he's no delicate flower as things come to blows with Adam Sandler in 1996's Happy Gilmore. After Gilmore's meteoric rise to professional golf fame, he chokes while playing on a team with Barker in a high-stakes tournament. Barker is his sassiest self as things start to get mean on the green. Showing off a killer left jab, he punches Sandler in the face over and over, before throwing him into a pond and beating him some more. As an extra bonus, he calls Sandler a "bitch" before strutting away, victorious.

Not only did the appearance boost ratings for The Price is Right, the fight earned Happy Gilmore an MTV Movie Award for Best Fight Scene. Barker's appearance was so iconic that not only was he approached about it daily, but the pair were approached by Comedy Central to re-enact the fight nineteen years later on their Night Of Too Many Stars, to great acclaim.

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From Al Pacino in Jack and Jill to Johnny Depp and Peter DeLuise in the 21 Jump Street film adaptation, a cameo appearance can push a movie over the top, for better or worse. What are your favorite movie cameos? Hit us up in the comments below!