Continuity mistake: When Shrek and everyone else are trying to get into the castle, shots of Shrek facing back toward the other side of the drawbridge are missing the others, i.e. the pigs, Wolf, Donkey, Puss, Pinocchio, and mice.
Continuity mistake: When the door to Shrek's house is first opened (just after the honeymoon), it opens into the house. Every other time it opens to the outside. It's not a two-way door, because you can hear it hit the doorframe.
Audio problem: When the Fairy Godmother sings "Holding Out for a Hero" she tells the pianist to 'put it in C minor,' yet the pianist immediately begins to play in G minor, and the rest of the song is sung in that key.
Continuity mistake: When Puss is getting the Happily Ever After potion from behind the glass, the piece of glass he cuts out to pull the potion through disappears when the camera angle changes.
Continuity mistake: When Fiona shows her fighting talent by saving Shrek, they approach the trap holding hands, yet Fiona is not even visible in the medium range shot when Shrek is caught.
Deliberate mistake: When Shrek first meets Puss In Boots, Puss In Boots bursts out of Shrek's clothes "Alien" style leaving a tear. Then when we see them enter the Fairy Godmother's factory the tear is gone for the rest of the movie.
Continuity mistake: When Shrek, Donkey and Puss all go to the barn to shelter themselves from the rain, the doors open inward. Later, after the potion has taken effect and Donkey's showing off his trotting ability, the doors open outward.
Continuity mistake: At the dinner scene, Shrek says "better out than in" to Fiona. After that, the handwashing bowl and the shell's plate suddenly changes.
Other mistake: This is a UK/US vocal talent variation. In the UK version the voice of the Ugly Stepsister is that of UK TV/Radio Presenter Jonathan Ross yet the vocal talents are credited as CNN talk show host Larry King. Also, the voice of the Red Carpet Reporter is none other than UK Pop Idol Extra presenter Kate Thornton, yet again, the voice is credited as Hollywood reporter Joan Rivers, whom the physical appearance of the character is based on.
Continuity mistake: Puss saves the Gingerbread Man from drowning in the castle's moat by catching him with his sword, however, he is on Donkey's back and the drawbridge is a couple of meters above the water. So the sword would have to have been 2-3 meters long to get down to the Gingerbread Man.
Continuity mistake: Fiona enters the study while her parents are drinking tea to tell them she's leaving. The doors are both wide open behind her and the hallway is completely clear. But when she leaves the room, she reaches down and picks up her suitcase in the hallway, which would have been visible behind her moments before.
Audio problem: When Fairy Godmother is lying on the piano using her wand as a microphone and singing about tossing and turning, sometimes Kyle's hands don't match the sounds of the piano. This is especially visible in very last shot - just before she says "Hit it", Kyle raises one hand and then we hear a part requiring both hands.