For many tweens of the 2000s, Club Penguin was the place to be. Players created penguin avatars, dressed them up, and roamed a virtual world of igloos, ski lodges, and mini-games. There were puffles, Tamagotchi-like pets to care for, and bustling servers where you could chat with friends, surf through a mine, or lob a virtual snowball at a stranger. At its peak, the game drew hundreds of millions of users and offered an early taste of social media for a generation of kids. Disaster struck in...