Continuity mistake: Rumplestiltskin looks completely different in this movie than he did in the previous film Shrek The Third; Prince Charming momentarily talks to Rumplestiltskin in the tavern during the third film, and the character looks completely different, has a different voice and different demeanor.
Continuity mistake: In the scene where Shrek goes back to the swamp after signing the contract, he realizes that Fiona isn't there and pulls out the contract to read it. He then notices something flying overhead and looks up to see the witches. In the next shot, we see no contract in Shrek's open hands.
Plot hole: In the first film it takes Shrek and Donkey several days to get to Fiona and then several days to get back to Duloc. In this film, Shrek only has one day as an ogre, yet he still manages to get to and from the castle that Fiona was locked in.
Continuity mistake: In the scene when Pinocchio arrives to request Rumpelstiltskin to convert him into a real kid there's nothing on the table but goblets and kind of cakes, after Rumpelstiltskin asks to the wolf his wig, he suddenly takes the contract from the table and on it appears the feather and ink that Pinocchio uses to sign the contract.
Plot hole: In the second Shrek movie, we find out that Fairy Godmother and the King had a deal that Prince Charming would save Princess Fiona from the keep, hence becoming her true love and breaking the curse. In the fourth movie, we start with Rumple monologuing about how he almost had the Kingdom by signing a deal with the King. Why would the King be so desperate to try and reverse the curse by signing a deal when he knows he has a prior attempt through Prince Charming, assuming it would take the same time for the messenger to return with news about Charming and Fiona either way?