Nickelodeon, the American cable and satellite TV network aimed at kids and teens, has introduced its first animated “gay married” couple. Debuting in The Loud House — a cartoon about Lincoln Loud, an 11-year-old boy with 10 sisters — the scene features a friend coming for a stayover with Lincoln. Lincoln and his chum, Clyde McBride, have been counting down the time to the sleepover, so perhaps that’s why Lincoln announces: “Time to make history!” — before he opens the door to reveal Clyde and his two dads. Owned by Viacom Media Network, Nickelodeon targets children ages 2 to 17....