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.
Continuity 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.
Plot hole: It is apparent that Shrek and Donkey have never traveled to the land of Far Far Away, yet Donkey immediately recognizes the "old Keeblers' place" when he should have no idea where it is or what it looks like.
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.
Other mistake: When Shrek, Donkey and Fiona first travel to Far Far Away Land, the shots and dialogue imply that it takes a few days to get there. Or at the least, several hours.When Pinocchio, Gingerbread Man and others go to rescue them, they arrive within the space of one or two songs at the concert.
Continuity mistake: When the cooks arrive with the food during the dinner scene they set the food down on the table, but in the next shot from above they are still walking towards the table with the food.
Other mistake: When the royal messenger informs Shrek and Fiona about the royal ball the scroll he is reading from is not open enough for him to be able to say what is written.
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.
Other mistake: In the scene where Shrek wakes up to find himself human in the barn, Puss is holding the potion bottle, reading its disclaimer. What is wrong, is the shadows on the floor (casting behind him) don't match the shadows on his body (casting to the right side).
Continuity mistake: When the request is made by the messenger to have Shrek and Fiona come to Far Far Away for the wedding party, as the trumpeteers troop off in the background you can see their footprints on the ground. However, when the same view is shown again seconds later the footprints are gone.