Parents often underestimate the corruptive nature of toy trains. Too concerned about the antisocial influence of Dungeons & Dragons, Tetris, and stamp collecting, they let their guard down for the minicaboose. It starts innocently, with a vintage Lionel setup, complete with a tunnel, a windmill, and a general store. But soon, little Johnny’s megalomania will be chugging ahead at full steam. Before you know it, a damsel in distress will be lying on the tracks, and (oh, no!) here comes the Santa Fe Express. Thirty years later, he’ll still be camped out in the basement, wearing his overalls and conductor’s hat and scaring the neighbors’ children. You’ll be desperate to get him out of the house. Fortunately, the Smithsonian has an outlet for locomotive shut-ins: “Great Railway Journeys,” an all-day seminar about trains featuring travel writers, railroad historians, and a “virtual front seat” on the California Zephyr. The trip begins at 9 a.m. at the Ripley Center, 1100 Jefferson Drive SW. $65. (202) 357-3030. (Felix Gillette)