Love them or hate them—the elves’ empire is growing. In less than two decades, the Elf on the Shelf book and kit has become as ubiquitous as—dare we say it? OK, we’ll say it—Santa Claus. The cheerful elves (or weird elves, depending on which camp you fall into) have appeared as a WK Kellogg’s Co. cereal, as a balloon in the Macy’s Inc. Thanksgiving Day Parade, as a toy in McDonald’s Corp. Happy Meals in Europe and in four Netflix Inc. specials. This year the elves were even featured in a cooking show on Warner Bros. Discovery Inc.’s Food Network.