Ok, so at the part when the human Shrek is using Mongo (the giant Gingerbread man) to storm the castle and save Fiona from falling under the love potion, I noticed an interesting little slip-up.
As Mongo's arms are breaking apart (because of the liquid poured on them), Shrek runs up Mongo's RIGHT (<== important!) arm and just manages to jump through the gap into the castle before the drawbridge closes.
Note: He SHOULD be sliding down the chain on the right side, correct?
Anyway, a moment later, it cuts to a clip of Shrek sliding down the chain inside the castle... ON THE LEFT SIDE.
This isn't really an important slip-up, but I notice it every time I see this movie and, personally, I find it amusing.