I would use this movie in my English Lit class.
Back when I taught 12th grade English, we'd read "Sir Gawain and the Green Knight" in my class. After we'd read the poem, I'd roll about the first 20 minutes of this film (the only part that had anything to do with the poem).
Before I hit "PLAY," I'd give the film a big build-up, calling it a "lost classic" with effects that were "ahead of their time," etc. Then I'd roll the film and watch the kids as Connery picked up that ridiculously-fake head and have a good laugh at it all.
"And me? I go on to become a big star in Italian Westerns."