Continuity mistake: When the girl gives Litwak her phone to show him there is a replacement part on eBay, her phones shows that it is connected to WiFi. Litwak doesn't set up his router until later that evening, he has only plugged it in. (00:09:41)
Factual error: While bidding on eBay for the steering wheel, Vanelope tries to up the $350 bid by bidding $1,000. This scares off the real bidder, but Ralph and Vanelope don't understand how eBay works and bid against each other until they win with a $27,001 bid. That's not how eBay works. Vanelope's initial $1,000 bid wouldn't have set the high mark, but would simply have been her maximum bid in case the other bidder kept increasing his bid. The current high bid would have increased by the increment amount until it reached Vanelope's max bid. Now, it could be that the system recognized Ralph and Vanelope as separate bidders and that's why it let them keep upping the max bid. But, if the system had responded normally and simply increased Vanelope's bid to $355 with a max of $1,000, they might have realised what was going on and not started bidding randomly.
Other mistake: Vanellope steals a car from the Slaughter Race game and speeds off. Shank, the main character of the game, commandeers another car and chases Vanellope. When Shank's car is seen in Vanellope's rear-view mirror, the image is not reversed. Shank appears to be driving from the passenger seat.