In the song 'The King is in the Altogether", Hans twists his cap to one side and this is shown in close-up. In the next long-shot the cap is immediately straight again.
Following his visit to the newspaper office, where he got a small paper page showing his name and story "The Ugly Duckling", Hans shows it to Peter. The headline appears closer to the left side of the page. But when next seen the headline is closer to the right side of the page, and neither Peter nor Hans have turned or rotated the page at all.
During the "Wonderful, Wonderful Copenhagen" song the concertina player directly behind the singer never moves his fingers on the keys.
The date on the poster for The Little Mermaid ballet is Saturday evening September 10, 1832, but that date was actually a Monday, not a Saturday.
In the 'Thumbelina' scene where Hans licks his right thumb and presses it against his left thumb to make a 'playmate' for Thumbelina, the faces are not mirror opposites. In fact, the 'new playmate' has a nose and a big smile that Thumbelina lacks.
During the crossing of the Great Belt the still existing light tower on the island Sprogø is seen in the background. Although there was a light tower on the island when the 14 year-old Hans Christian Andersen went to Copenhagen, this particular tower was not built until 1869, when Andersen was 64 years old and had been a famous writer for many years.
When Hans Christien Andersen and Peter cross the Great Belt, Peter spots Copenhagen on the other side of the belt, but Copenhagen is located on the other side of Zealand and cannot be seen from a boat on the Great Belt.