Factual error: In the opening shot of the film, The first verse of the poem is recited. There is a very minor mistake in the subtitles on the region 1 DVD. Instead of "...in the wabe: All mimsy..." they read "...in the wabe. All mimsy...". (00:00:10)
Factual error: As the knight and Dennis leave to fight the Jabberwock, another verse of the poem is recited. A line is read as "the Jabberwock with eyes aflame". The line in the original poem is "the Jabberwock with eyes of flame". (01:22:30)
Factual error: In his fight against Dennis and the Jabberwocky, the Black Knight uses a flamberge, a very distinct two-handed sword (note the little "crescent" hooks on the blade). The only problem is that these swords are a German design from the 15th century, more than 200 years after the movie is said to take place.
Factual error: The movie takes place in a Medieval European setting. This general historical context is strictly observed, but with one exception: the potato. Potatoes are part of the so-called Columbian exchange. There were no potatoes in the Middle Ages.