The mask Michael wears is the exact same mask (a repainted and modified Captain Kirk mask) worn in the original La Nuit des masques (1978) film. It looks different in the sequel because the paint had faded due to a few reasons, first because Nick Castle, the original Michael, kept it in his back pocket during shoots. Also, Debra Hill kept the mask under her bed for several years until the filming of Halloween II, causing it to collect dust and yellow because Hill was a heavy smoker. Also, the mask appears wider because Dick Warlock is shorter and stockier than Nick Castle, so the mask fit his head differently. As the producers thought it would be the final sequel in the series, they let Warlock keep the mask, scalpel, boots, jumpsuit, and knife used in filming. When they decided to revive Michael in Halloween 4 : Le Retour de Michael Myers (1988), the producers realized they had made a mistake and never again gave props out to the cast and crew, therefore subsequent sequels used different masks that looked rather different.
To get the role of Michael Myers, Dick Warlock revealed that as he passed by a room, the Michael Myers mask was on a table. He put the mask on and walked into Rick Rosenthal's office and stood there. After Rosenthal continuously asked him who he was and he didn't reply, he took off the mask and asked if he could play Michael Myers.
(at around 11 mins) The voice of Alice's friend (heard over a telephone) is the voice of Nancy Loomis, who played Annie in La Nuit des masques (1978), and appears in "Halloween II" as the corpse of Annie.
The film was bookended by the song "Mr. Sandman" sung by The Chordettes. The tune would also later be used in the later Halloween movies Halloween, 20 ans après (1998) and Halloween (2007), although the latter featured a cover version by Nan Vernon.
The film is set immediately after the first La Nuit des masques (1978). Since Jamie Lee Curtis had begun to wear a much shorter hairstyle in the 1980s, she had to wear a wig that matched her original hairstyle for the film.