Bella Challis, played by Michelle Walker, is a character in the film Halloween III: Season of the Witch
Bella's father Dr. Daniel Challis comes home with Halloween masks for her and her brother Willie; however, their mother Linda already bought them some.
They show off their Silver Shamrock brand masks that are all the rage. The rush to turn on the television hoping to catch the teaser commercial for a Silver Shamrock Halloween Giveaway.
After Dr. Challis discovers the nefarious plot by Conal Cochran, he desperately calls the television stations to not air the commercial. After having a couple channels pull the commercial, another still allowed it to play. Knowing both Bella and Willie were looking forward to the giveaway, they likely watched the lethal commercial.