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.
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.