1 Malcolm McDowell's eyes were anesthetized for the torture scenes so that he would film for periods of time without too much discomfort. Nevertheless his corneas got repeatedly scratched by the metal lid locks.
2 The snake, Basil, was introduced into the film by Stanley Kubrick when he found out Malcolm McDowell had a fear of reptiles. This was to make McDowell's character seem more intimidating, and as a practical joke by Kubrick.
3 According to Malcolm McDowell (on the commentary track from the 2007 DVD release), the sped-up sex scene was originally filmed as an unbroken take lasting 28 minutes.
4 When Malcolm McDowell met Gene Kelly at a party several years later, the older star turned and walked away in disgust. Kelly was deeply upset about the way his signature from Singin' in the Rain (1952) had been portrayed in A Clockwork Orange (1971).
Wow. But really, why hold it against Malcolm McDowell? It's not like he did anything legitimately wrong. - Elric-san
I don't blame him. - Britgirl
5 Stanley Kubrick's first cut (before hiring several assistant editors) ran almost four hours
6 The doctor standing over Alex as he is being forced to watch violent films was a real doctor, ensuring that Malcolm McDowell's eyes didn't dry up.
7 Stanley Kubrick had his assistant destroy all unused footage.
Too bad. Would have made interesting viewing, especially since his first cut would have included much more than the finished work. - Billyv
8 Although he is playing a 15-year-old (17 in the latter half), Malcolm McDowell was actually 27 at the time of filming.
I always thought he looked much older than the character, but it wasn't distracting and didn't affect the viewing. - Billyv
9 The final scene was done after 74 takes.
10 During the filming of the Ludovico scene, star Malcolm McDowell scratched one of his corneas and was temporarily blinded. He suffered cracked ribs during filming of the humiliation stage show.