One thing everyone should know about Chris Pratt is that he was born to play Star-Lord. During the scene when he offers the Orb to the Collector, he drops it, picks it back up and pretends nothing went wrong. This wasn't in the script, but director James Gunn liked it and thought it was consistent with the character, so he kept it in.
This is another instance of the director liking a goof. It doesn't hurt that the writer and director were both the same person here. After former hand model J.P. Prewitt gives an epic monologue about why male models are being used as assassins, Zoolander repeats his line, "But why male models?"
Ben Stiller honestly forgot his line, but actor David Duchovny went with it and it made for an extra laugh.
This film is book-ended by Honey Bunny and Ringo attempting to hold up a diner. Though we see the same action twice, Honey Bunny shouts two different lines. When director Quentin Tarantino noticed this he decided to keep it, as it showed a shift from Honey Bunny and Ringo's point of view to that of Jules and Vincent.
When Count Rugen takes Westley hostage, he knocks him out using the butt of his sword. Unfortunately, they only had real swords, so when actor Christopher Guest bonked Cary Elwes on the head, he knocked him out for real. They kept the shot, as it unsurprisingly looked mighty authentic.
Actor Viggo Mortenson insisted on performing many of his own stunts. This wound up biting him in the ass. Or, more accurately, the foot. During a scene where he kicks a helmet in despair, the actor kicked the helmet multiple times to get it to look just right. On the take they used, he wound up breaking two of his toes.
Here's another example of an actor paying the price for doing their own stunt. While running through the woods, James Franco ran into a tree and fell to the ground in agony. This wasn't acting. He split his forehead open and required stitches. The character wears a headband for the remainder of the movie to hide this.
This fight scene between Sonny and Carlo is criticized for looking fake, but one of the actors sustained a real injury. Gianni Russo received multiple broken ribs courtest of James Caan. Caan was said to not be a fan of Russo's, and even improvised the part where he bashes him with a trash can lid.
Remember that flash of fire when the Wicked Witch makes her exit from Munchkinland? That wasn't planned. The actress received first and second degree burns as her copper makeup heated up. They had to use the imperfect take and give the poor woman time to heal. This has to be one of the most terrible costume mistakes in movie history.
They literally made a movie about everything that went wrong with making this movie. As revealed in the documentary Hearts Of Darkness, Martin Sheen was heavily intoxicated during his opening scene. He punches a mirror, which wasn't planned, and sliced his hand open. That's real blood you see onscreen.
Channing Tatum gave a powerful portrayal of wrestler Mark Schultz. In one of the more visceral scenes, while punching himself in the face in front of a mirror, he gets even more intense and bashes his head into it several times, shattering it and even the drywall behind it. Again, this was not planned, and he cut his forehead wide open.
Maybe actors should just stop breaking glass onset? Leonardo DiCaprio broke a glass when he slammed his hand on a table. Director Quentin Tarantino loved the take, and shot the remainder of DiCaprio's scenes with his character wearing a bandage on his hand.
Yet another example of glass and actors doing their own stunts gone wrong. In the scene where Pris is making a getaway, actor Daryl Hannah slipped and slid into a car, smashing the window with her elbow. It wasn't planned, but looked good, so they kept it. It was later learned Hannah chipped her elbow in eight places.
Enough with actors getting hurt. How about a little levity. In this line-up scene, the actors weren't supposed to start laughing. Director Bryan Singer was actually annoyed, but wound up liking it once he saw the footage.
The reason the actors were all laughing? Benicio Del Toro couldn't hold in his flatulence.
During the opening scene when Stormtroopers board a rebel ship, one of the taller ones bonks his head on the door. In later versions of the movie, George Lucas would even add a sound effect, making it all the more obvious and hilarious. This has to be one of the most well-known movie mistakes, as Star Wars fans have a tendency to get quite immersive with their fandom.