Continuity mistake: When Emmet goes to buy overpriced coffee, Larry the Barista says "That's 37 bucks." In the background, you can see a woman in a Fabuland T-shirt is right next to the window. When Emmet replies "Awesome!" she has moved a (Lego) metre forward and someone is opposite her. (00:05:05)
Continuity mistake: When Emmet and Wyldstyle ride in The Wild West, Wyldstyle's horse changes from black to brown and then back to black. (00:19:00)
Continuity mistake: After crashing the pig drawn car the characters fall onto a train car, the rail car directly behind the one they fall on is open and carrying barrels. In the very next scene none of the characters have moved, but there is now an enclosed train car there. (00:35:25)
Continuity mistake: During the chase scene in the Wild West, Bad Cop shoots a tracking device onto the back of Emmet's left leg. The tracking device disappears and re-appears at random until it is revealed during the attack by Bad Cop on Cloud Cuckoo Land.
Continuity mistake: In the real world, the dad seems to take apart a whole bunch of the son's creations and put them back to the way they were before. But in later shots, none of the son's creations seem to have changed.
Continuity mistake: Wyldstyle and Unikitty are seen falling out of a spaceship with space clothes on, and upon their landing are cornered. The next time they are seen they are still cornered, wearing their normal clothes.
Continuity mistake: While in the custody of Bad Cop, Emmet is chained by both hands to the melting apparatus. But when Wildstyle frees him, she only chops one chain to do so.
Continuity mistake: When Emmet and Wyldstyle go through the tunnel from Bricksburg to The Old West, they fall through with the bricks from the creation. When they fall out of the portal the bricks are gone.
Answer: There's not actually a reason. Don't forget, this is just played out in a father and child's imagination. The father and child are just imagining the story as they go along,.
Casual Person