Continuity mistake: The screen doors on the Darlings' front doors appear and disappear between scenes. Also, with double doors, one door is bolted shut with top and bottom latches most of the time ("inactive") with the other door being the "active" door that is opened and closed when coming or going. However, throughout the film characters open either door, which would be impossible to do without interfering with the lock mechanism, the door stop mouldings, etc. and damaging the doors' edges.
Continuity mistake: When Jim Dear is at the kitchen table reading his torn morning paper, he reaches through the front page to grab his cup of coffee from a plate. But in the next shot where Lady is at his feet wagging her tail in anticipation for some coffee, a piece of toast and butter knife suddenly appear from nowhere among the other items on the table.
Continuity mistake: During Tramp's walk through town on a search for breakfast, he notices a few puppies for sale and takes a moment to admire them. The hands of the downtown clock behind his left shoulder are positioned at 7:00 A.M., but when Tramp turns away and resumes walking the clock reads 1:00 P.M.
Continuity mistake: When Trusty is having a dream on his porch, a striped caterpillar makes his way down from a potted plant on the front door's right side. So Trusty - still asleep - sniffs his way along the porch's floorboards where the caterpillar falls between a crack. Suddenly he wakes up to see Lady and Jock waiting at the staircase. In the next shot he's asking which way the caterpillar went, but if you look at the plant behind him you can see how it's now placed on the door's left side instead.
Continuity mistake: After Jock and Trusty stop the pound carriage in its tracks, an oncoming taxi illuminates the back where Tramp is locked up. Here we can see the door's cage has no broken metal wires, but two shots later where Lady walks up to it, a couple of its wires are suddenly sheared apart.