Continuity mistake: Sometimes Shrek's front door opens outwards, at other times inwards, yet it can't be "two-way" because whenever it closes, it slams against the frame. (00:10:55 - 00:13:45)
Continuity mistake: In the scene immediately following Fiona's thrashing of Robin Hood and his Merry Men, Shrek is holding Donkey and they are staring at Fiona in disbelief. When Shrek drops Donkey and turns to follow Fiona, you can see his entire backside and it's unpierced. In the next scene, Fiona discovers an arrow in his rump that wasn't there before. (00:53:18)
Continuity mistake: At the end of the film, the three blind mice are turned into the horses for the onion carriage but a second later they are dancing on the piano. (01:21:10 - 01:22:00)
Continuity mistake: At the start of the film, Shrek is painting his "Ogre Beware" sign, you will notice that quite a bit of the top left corner of the board is missing. When he hangs the board on the post it is the opposite corner that is gone. He did not paint on both sides. (00:02:35)
Continuity mistake: The dragon flies down without a chain, then there is a chain dangling for Shrek to climb about to go to the castle, and while the dragon is flying, the chain is gone again. (01:14:05)
Other mistake: When a glass of milk is poured, if you look closely, the glass is filled but the level of milk in the bottle doesn't seem to lower. (00:16:00)
Continuity mistake: In the scene where Donkey and Shrek are crossing the bridge to rescue the princess, Donkey trips and breaks a board. In subsequent shots sometimes you can see a little bit still stuck in the ropes, and sometimes it disappears. (00:30:35)
Continuity mistake: When Lord Farquaad announces Shrek as champion, there are flagposts surrounding them. In the close-up of Shrek and Donkey, these flagpoles have disappeared, as have the shields on the walls that the flagpoles stand on. (00:24:35)
Revealing mistake: When Shrek and Donkey are sitting by the fire and looking at the stars, when Donkey asks Shrek about "our swamp" and Shrek says "We?" When Shrek blinks, his right eyeball is slicing through his upper lid. (00:46:30)
Continuity mistake: In the scene where Shrek and Donkey are on the wooden bridge, when Shrek starts rocking the bridge, we see that the castle is still quite a way off. However, Donkey only takes a few steps to get to the end.
Continuity mistake: When Shrek backs into the two barrels at the tournament, they both have taps on them. He then bashes one of these off with the beer mug. But when Donkey rolls the other barrel the tap has vanished on that one as well. (00:24:00)
Continuity mistake: In the scene where Farquaad's men are chasing after Donkey and run into Shrek, their leader is holding a scroll. In the next shot, it completely disappears without him moving it at all.
Revealing mistake: When Donkey first meets Shrek, when Shrek confronts the knights, not all the shadows fall the same way. Shrek's shadow is cast forward onto the leader knight, whereas the knights' shadows are off to their left.
Continuity mistake: On the bridge over the lava, when Donkey steps on one of the boards, it breaks down the middle into two pieces. But when we see it falling, it's the entire board as if it had come off without breaking. (00:36:30)
Continuity mistake: During the scene where Fiona pulls the arrow out of Shrek, Donkey faints. When he hits the ground about 6 leaves float up from the ground as if Donkey had fallen into a pile of leaves. When we next see Donkey laying on the ground and when Shrek picks him up, there are no leaves on the ground, they disappeared.
Factual error: As Shrek is sitting near the sunflowers field and staring at the Duloc (and day becomes night), we don't see the cathedral anywhere. It should be visible as such a big building, due to how big it is seen later, it should be very distinct over the houses' roofs.
Continuity mistake: When Shrek is announced champion, there are awnings above the audience which cause parts of the audience to be dark, but when we see a close-up of Donkey and Shrek there is no darkness, meaning that the awnings have disappeared.
Continuity mistake: The sun sets in different directions with respect to the same view of Lord Farquaad's castle.
Continuity mistake: When Shrek and Lord Farquadd are talking about the swamp after Shrek has just beaten all of his knights, the flags move across the wall between shots.
Continuity mistake: When Shrek walks out of his house and finds the fairytale creatures, you can see the three fairies go into one of the tents that were set up. The shot goes back to Shrek for a minute and then goes back towards the crowd and the fairies are back in the place that they were before.
Chosen answer: This is most likely because "broad" isn't too nice of a word, and children of any age could watch the trailer. Parents wouldn't want their children to copy inapropriate language, obviously.