When the children’s TV series “Teletubbies” premiered in 1997 in the U.K.—and a year later in the U.S.—the oldest members of Gen Z were just being born. Many Gen Zers grew up alongside the show’s four colorful creatures, Tinky Winky, Dipsy, Laa-Laa and Po. More than two decades later, the series’ parent company, WildBrain, is harnessing social media to reach that same audience at a new stage in their lives.