In the truck, when Gertie soils herself, one of the boys says that from now on she will be known as "Dirty Girtie." However, although this rhymes when spoken in English, the characters where speaking Dutch, with English subtitles shown, and it does not rhyme in Dutch, which is clearly what was intended for humorous effect.
Although the story takes place during World War II, the backdrop set used in the show that the Canadian soldiers put on for the townspeople features a red-and-white maple leaf Canadian flag, not adopted until 1965.
Although the story takes place in 1944, the house which Jeroen leaves from in 1944 clearly has modern thermal pane windows.
While the film purportedly takes place in 1945, the song Sh-Boom that Jeroen and the soldier dance to was not written until 1954, nine years later.