Gary Oldman wore Sid's real chain necklace in the movie. When doing his research, Sid's mom gave him the necklace to wear during filming.
Gary Oldman lived on a diet of steamed fish and melon to lose enough weight to play the emaciated, heroin-addicted Sid, and was hospitalized when he went too far and became malnourished.
To prepare for the scene where Nancy smashes a phone booth, the crew had replaced a few panes of glass with fake glass. However, Chloe Webb was so caught up in the moment that she broke several of the real glass panes, too, and was lucky she didn't get cut up.
According to Gary Oldman, he disliked the script, and dislikes punk music, but he accepted the role because of the salary, which was £35,000.
The real Johnny Rotten (John Lydon) dismissed this film as "mere fantasy . . . the Peter Pan version."