When Wreck-It Ralph realizes he is in the Sugar Rush game he says, "This is the candy go-cart game over by the Wak-A-Mole." However, at the beginning of the movie, as the camera rolls away from the Fix-It Felix Jr. cabinet, the game next to Sugar Rush says Wak-A-Troll.
During the race sign up scene, when each racer is throwing their coin into the gold cup as the entry fee, the announcer says Snowanna Rainbeau, and you can see a blue haired pig-tailed character just behind Rancis Fluggerbutter. This character is Citrusella Flugpucker, the 6th listed racer on the board, but she is announced as Jubileena Bing-Bing, who is listed 13th on the board. Jubileena Bing-Bing is the red pig-tailed racer, not the blue.
When the Sugar Rush racers are throwing in their gold coins to enter the Random Roster Race, the announcer can be heard reading the name "Adorabeezle Winterpop" third, after Taffyta Muttonfudge, and "Crumbelina Di Caramello" fifth, after Gloyd Orangeboar. But the next time the roster board is shown, Crumbelina's name is printed on line 3, while Adorabeezle's name is on line 5. The board's order may be considered the correct one, as not only does the same order appear on it again as the race commences, but Crumbelina can be seen lined up right behind Taffyta just before they begin to toss their coins to the pot.
Vanellope's Kart has a strawberry on the front right wheel and a lemon on the front left; the rear wheels are just cookies. Best view of the lemon occurs when King Candy flips Vanellope's kart in the tunnel. When Vanellope crashes just before the finish line, the front wheels have switched sides. The lemon(now right wheel) departs during the crash and the strawberry is shown as the front left wheel.
When Deanna begins to pull Felix onto the dance floor, she is wearing a shiny dress imprinted with leaves and flowers. When they take their places in the next shot, Deanna is suddenly in a plain pink dress, with no imprints. Then, although she remains on the dance floor for the entire shot, when Gene answers Felix in the very next shot, Deanna is suddenly with Gene by the door, and she's back in the dress with the shiny imprints for the rest of the scene.
When Vanellope crashes just before the finish line, the color pattern of her kart's six straw exhausts are different before and after the arrival of Felix and Ralph. The "after" color pattern is the correct pattern that matches the rest of the movie. The "before" color pattern seems to have the left and right exhausts swapped.
Before the final race begins there are 14 karts standing at the start line (including the King's empty kart), while according to the board there should be 15 (excluding the "no show" Vanellope). The one missing racer is Sticky Wipplesnit.
Ralph's first game in Hero's Duty happens just after the arcade opens. By the time Ralph gets to the top of the tower (which is implied to be before the next game starts by the "Quarter Alert" heard at the end of the first game), the arcade has closed.
When Ralph smashes the cake, Mary is seen standing behind Gene. She's not holding anything during the smashing, but as Ralph begins to leave the party the camera shows Mary holding onto the cake figurines which would have been smashed previously.
When King Candy visits Ralph to tell him to stop Vanellope from racing and gives him his Hero Medal, Ralph stuffs it in his overalls. The blue ribbon of the medal is not visible on a number of shots until Vanellope spots it and then the blue ribbon is visible.
After Ralph destroys the cake and it goes all over the place, we cut to a wide shot. In this shot, to Gene's right, there is a small amount of cake on the floor. In the following shot, the amount of cake has doubled.
When Ralph gets trapped in the cupcake and is at King Candy's castle talking to him, the Oreos are behind King Candy and pointing spears at Ralph. However, when the shot switches to Ralph and back to King Candy, the Oreos aren't pointing their spears at Ralph but just holding them. When King Candy dismisses the Oreos, they pull back their spears as if they had just finished pointing them and walk away.
Ralph says he gets a perfect view of the game Sugar Rush when he is lifted at the top of the building, as if he cannot see it from a lower position. In a previous scene, though, he can perfectly see the game from a balcony. However, Ralph would be unable to watch Vanellope race from the balcony during in-game hours, like she had wanted, and being lifted by the Nicelanders is the only way to for him to view Sugar Rush if there is someone playing his game.
When Ralph doesn't appear in his game, Felix climbs off the side of the building and exits the screen. In the next shot, he is just seen exiting the light source. Evidently, the light source is wider than the screen (so Felix is still in the light but already off-screen), which actually make sense even in the real world, since the inside of the game is illuminated from various angles.
When Ralph emerges from the chocolate milk after avoiding the police and devil dogs he is completely dry. He should be completely soaked. This is, however, assuming that Sugar Rush would have a realistic physics engine, or that Ralph, being a character from a different game, would be affected by it; Vanellope is pushed into the mud later on yet also remains completely dry and clean.
When Ralph approaches the candy tree on which his medal is stuck, the camera shows a rising shot of the whole tree from bottom to top, then a shot looking down the tree from near the top, but neither Vanellope nor any double stripe branches can be seen in these shots, even though they both appear seconds later when Ralph climbs the tree. However, for all we know the double-stripe branches can appear out of nowhere (since they disappear, they can also reappear, why not). As for Vanellope, she repeatedly demonstrates the ability to move at blinding speeds up and down the tree throughout the scene, so she had plenty of time to jump to the branch while Ralph was climbing the tree.
At the start of the movie, "Fix-it Felix Jr" is at the back of the arcade and facing the door and "Sugar Rush" is two or three machines down, while at the the end of the movie "Fix-it Felix Jr" is facing "Sugar Rush" directly. However, the opening sequence establishes that games are often moved within the arcade, and since "Fix-it Felix Jr" suddenly became more popular, it makes perfect sense that it was moved to a more central location.
The double-striped candy branches vanish at different time intervals after being touched: 3 seconds (after Ralph first touches one), 1 second (twice, as Ralph and Vanellope race for the medal), 35 seconds (before Ralph falls into taffy), and 11 seconds (before Calhoun and Felix fall into quicksand). Evidently, this time interval is variable, rather than constant. Makes sense too - less predictable behavior makes the game more interesting.
Vanellope uses a medal that Ralph took from Hero's Duty to pay her fees and enter the Random Roster Race, after which it is shown dissolving into the game's code until retrieved by King Candy later on. In a real program a code from another game introduced like that would probably be incompatible and could crash the program, but in the reality of the movie it is allowed, since the entire plot is based on the premise that programs can jump from one game to another and interact fully and seamlessly with any foreign game.
The Fix-It Felix Jr. arcade game features characters with digitized voices. The technology for digitized speech in arcade games didn't arrive until 1983, while the game was supposedly installed in 1982. However, this supposition is based on the assumption that the "present year" is 2012 (the year the movie came out), which is not necessarily true - the exact year is never mentioned in the movie, so there is no definitive anachronism here.
When King Candy enters the code room he goes out in the direction of Vanellope's code box, but in Sour Bill's flashback King Candy's rope is to the left while he's pushing Vanellope's code box to the right, so it would appear that the scene was reversed. However, there are several plausible explanations for this: a) since the code room has no gravity and there is no definitive upward direction, the scene may be upside down in the flashback, in which case Vanellope's box position is correct, b) the box has changed position over the years (it is freely floating in space after all), c) there is another access port to the code room from a different direction, and d) Bill didn't recall the scene exactly right (which is plausible since his memory was partially blocked).
In the opening sequence, when Ralph is telling his life story, arcade closes and the camera travels through the Fix-It Felix console's screen. Being that nobody is playing the game, the title can be seen on the screen from outside, and, in a brief shot, within the game world, too. Later in the movie, when Ralph returns to the game and throws his medal at the back of the screen, that logo cannot be seen. This is because the game has been abandoned by that point. In particular, all the lights in the Nicelander's house went off. Evidently, the logo was shut down as well. Regardless, the logo doesn't have to appear all the time when the game is not used.
The goof items below may give away important plot points.
When Ralph looks down on the entrance of Sugar Rush after being lifted by King Candy, you can see the path is empty between Calhoun, Felix, Vanellope and the cy-bugs. But when Ralph frees himself from King Candy's grip and Vanellope starts glitching towards Ralph, you can see Calhoun's discarded weapon lying on the ground. Something so distinctly black would stand out on the rainbow bridge from a distance.
When Calhoun tells everyone to go to Game Central Station, the sign at the finish line reads 'FINISH'. A few seconds later, when Ralph looks up to a board with a map of the racetrack, we see the sign on the finish line still reads 'START', which flashes for a moment before reading 'FINISH'. He turns to the sign again, which has just started reading 'FINISH'.
Sour Bill tells Ralph that King Candy tried to delete Vanellope from the code and locked up the memories of everyone in the game. If that's true then Sour Bill shouldn't be able to remember King Candy's attempt at deleting Vanellope. He remembers because he was there and saw everything. At one point of the flashback King Candy is signaling someone off-screen to pull him back, and that someone could only be Sour Bill. When the memories were locked, he forgot why King Candy is doing this, but he could still see what he was doing.