The mask Michael wears is the exact same mask (a repainted and modified Captain Kirk mask) worn in the original
Halloween (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: The Return of 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.
